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    // This is a part of Chrono.
    // See README.md and LICENSE.txt for details.

    //! # Chrono: Date and Time for Rust
    //!
    //! It aims to be a feature-complete superset of
    //! the [time](https://github.com/rust-lang-deprecated/time) library.
    //! In particular,
    //!
    //! * Chrono strictly adheres to ISO 8601.
    //! * Chrono is timezone-aware by default, with separate timezone-naive types.
    //! * Chrono is space-optimal and (while not being the primary goal) reasonably efficient.
    //!
    //! There were several previous attempts to bring a good date and time library to Rust,
    //! which Chrono builds upon and should acknowledge:
    //!
    //! * [Initial research on
    //!    the wiki](https://github.com/rust-lang/rust-wiki-backup/blob/master/Lib-datetime.md)
    //! * Dietrich Epp's [datetime-rs](https://github.com/depp/datetime-rs)
    //! * Luis de Bethencourt's [rust-datetime](https://github.com/luisbg/rust-datetime)
    //!
    //! Any significant changes to Chrono are documented in
    //! the [`CHANGELOG.md`](https://github.com/chronotope/chrono/blob/main/CHANGELOG.md) file.
    //!
    //! ## Usage
    //!
    //! Put this in your `Cargo.toml`:
    //!
    //! ```toml
    //! [dependencies]
    //! chrono = "0.4"
    //! ```
    //!
    //! ### Features
    //!
    //! Chrono supports various runtime environments and operating systems, and has
    //! several features that may be enabled or disabled.
    //!
    //! Default features:
    //!
    //! - `alloc`: Enable features that depend on allocation (primarily string formatting)
    //! - `std`: Enables functionality that depends on the standard library. This
    //!   is a superset of `alloc` and adds interoperation with standard library types
    //!   and traits.
    //! - `clock`: enables reading the system time (`now`), independent of whether
    //!   `std::time::SystemTime` is present, depends on having a libc.
    //!
    //! Optional features:
    //!
    //! - `wasmbind`: Enable integration with [wasm-bindgen][] and its `js-sys` project
    //! - [`serde`][]: Enable serialization/deserialization via serde.
    //! - `unstable-locales`: Enable localization. This adds various methods with a
    //!   `_localized` suffix. The implementation and API may change or even be
    //!   removed in a patch release. Feedback welcome.
    //!
    //! [`serde`]: https://github.com/serde-rs/serde
    //! [wasm-bindgen]: https://github.com/rustwasm/wasm-bindgen
    //!
    //! See the [cargo docs][] for examples of specifying features.
    //!
    //! [cargo docs]: https://doc.rust-lang.org/cargo/reference/specifying-dependencies.html#choosing-features
    //!
    //! ## Overview
    //!
    //! ### Duration
    //!
    //! Chrono currently uses its own [`Duration`] type to represent the magnitude
    //! of a time span. Since this has the same name as the newer, standard type for
    //! duration, the reference will refer this type as `OldDuration`.
    //!
    //! Note that this is an "accurate" duration represented as seconds and
    //! nanoseconds and does not represent "nominal" components such as days or
    //! months.
    //!
    //! When the `oldtime` feature is enabled, [`Duration`] is an alias for the
    //! [`time::Duration`](https://docs.rs/time/0.1.40/time/struct.Duration.html)
    //! type from v0.1 of the time crate. time v0.1 is deprecated, so new code
    //! should disable the `oldtime` feature and use the `chrono::Duration` type
    //! instead. The `oldtime` feature is enabled by default for backwards
    //! compatibility, but future versions of Chrono are likely to remove the
    //! feature entirely.
    //!
    //! Chrono does not yet natively support
    //! the standard [`Duration`](https://doc.rust-lang.org/std/time/struct.Duration.html) type,
    //! but it will be supported in the future.
    //! Meanwhile you can convert between two types with
    //! [`Duration::from_std`](https://docs.rs/time/0.1.40/time/struct.Duration.html#method.from_std)
    //! and
    //! [`Duration::to_std`](https://docs.rs/time/0.1.40/time/struct.Duration.html#method.to_std)
    //! methods.
    //!
    //! ### Date and Time
    //!
    //! Chrono provides a
    //! [**`DateTime`**](./struct.DateTime.html)
    //! type to represent a date and a time in a timezone.
    //!
    //! For more abstract moment-in-time tracking such as internal timekeeping
    //! that is unconcerned with timezones, consider
    //! [`time::SystemTime`](https://doc.rust-lang.org/std/time/struct.SystemTime.html),
    //! which tracks your system clock, or
    //! [`time::Instant`](https://doc.rust-lang.org/std/time/struct.Instant.html), which
    //! is an opaque but monotonically-increasing representation of a moment in time.
    //!
    //! `DateTime` is timezone-aware and must be constructed from
    //! the [**`TimeZone`**](./offset/trait.TimeZone.html) object,
    //! which defines how the local date is converted to and back from the UTC date.
    //! There are three well-known `TimeZone` implementations:
    //!
    //! * [**`Utc`**](./offset/struct.Utc.html) specifies the UTC time zone. It is most efficient.
    //!
    //! * [**`Local`**](./offset/struct.Local.html) specifies the system local time zone.
    //!
    //! * [**`FixedOffset`**](./offset/struct.FixedOffset.html) specifies
    //!   an arbitrary, fixed time zone such as UTC+09:00 or UTC-10:30.
    //!   This often results from the parsed textual date and time.
    //!   Since it stores the most information and does not depend on the system environment,
    //!   you would want to normalize other `TimeZone`s into this type.
    //!
    //! `DateTime`s with different `TimeZone` types are distinct and do not mix,
    //! but can be converted to each other using
    //! the [`DateTime::with_timezone`](./struct.DateTime.html#method.with_timezone) method.
    //!
    //! You can get the current date and time in the UTC time zone
    //! ([`Utc::now()`](./offset/struct.Utc.html#method.now))
    //! or in the local time zone
    //! ([`Local::now()`](./offset/struct.Local.html#method.now)).
    //!
    //! ```rust
    //! use chrono::prelude::*;
    //!
    //! let utc: DateTime<Utc> = Utc::now();       // e.g. `2014-11-28T12:45:59.324310806Z`
    //! let local: DateTime<Local> = Local::now(); // e.g. `2014-11-28T21:45:59.324310806+09:00`
    //! # let _ = utc; let _ = local;
    //! ```
    //!
    //! Alternatively, you can create your own date and time.
    //! This is a bit verbose due to Rust's lack of function and method overloading,
    //! but in turn we get a rich combination of initialization methods.
    //!
    //! ```rust
    //! use chrono::prelude::*;
    //! use chrono::offset::LocalResult;
    //!
    //! let dt = Utc.ymd(2014, 7, 8).and_hms(9, 10, 11); // `2014-07-08T09:10:11Z`
    //! // July 8 is 188th day of the year 2014 (`o` for "ordinal")
    //! assert_eq!(dt, Utc.yo(2014, 189).and_hms(9, 10, 11));
    //! // July 8 is Tuesday in ISO week 28 of the year 2014.
    //! assert_eq!(dt, Utc.isoywd(2014, 28, Weekday::Tue).and_hms(9, 10, 11));
    //!
    //! let dt = Utc.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12); // `2014-07-08T09:10:11.012Z`
    //! assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_micro(9, 10, 11, 12_000));
    //! assert_eq!(dt, Utc.ymd(2014, 7, 8).and_hms_nano(9, 10, 11, 12_000_000));
    //!
    //! // dynamic verification
    //! assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(21, 15, 33),
    //!            LocalResult::Single(Utc.ymd(2014, 7, 8).and_hms(21, 15, 33)));
    //! assert_eq!(Utc.ymd_opt(2014, 7, 8).and_hms_opt(80, 15, 33), LocalResult::None);
    //! assert_eq!(Utc.ymd_opt(2014, 7, 38).and_hms_opt(21, 15, 33), LocalResult::None);
    //!
    //! // other time zone objects can be used to construct a local datetime.
    //! // obviously, `local_dt` is normally different from `dt`, but `fixed_dt` should be identical.
    //! let local_dt = Local.ymd(2014, 7, 8).and_hms_milli(9, 10, 11, 12);
    //! let fixed_dt = FixedOffset::east(9 * 3600).ymd(2014, 7, 8).and_hms_milli(18, 10, 11, 12);
    //! assert_eq!(dt, fixed_dt);
    //! # let _ = local_dt;
    //! ```
    //!
    //! Various properties are available to the date and time, and can be altered individually.
    //! Most of them are defined in the traits [`Datelike`](./trait.Datelike.html) and
    //! [`Timelike`](./trait.Timelike.html) which you should `use` before.
    //! Addition and subtraction is also supported.
    //! The following illustrates most supported operations to the date and time:
    //!
    //! ```rust
    //! # extern crate chrono;
    //!
    //! # fn main() {
    //! use chrono::prelude::*;
    //! use chrono::Duration;
    //!
    //! // assume this returned `2014-11-28T21:45:59.324310806+09:00`:
    //! let dt = FixedOffset::east(9*3600).ymd(2014, 11, 28).and_hms_nano(21, 45, 59, 324310806);
    //!
    //! // property accessors
    //! assert_eq!((dt.year(), dt.month(), dt.day()), (2014, 11, 28));
    //! assert_eq!((dt.month0(), dt.day0()), (10, 27)); // for unfortunate souls
    //! assert_eq!((dt.hour(), dt.minute(), dt.second()), (21, 45, 59));
    //! assert_eq!(dt.weekday(), Weekday::Fri);
    //! assert_eq!(dt.weekday().number_from_monday(), 5); // Mon=1, ..., Sun=7
    //! assert_eq!(dt.ordinal(), 332); // the day of year
    //! assert_eq!(dt.num_days_from_ce(), 735565); // the number of days from and including Jan 1, 1
    //!
    //! // time zone accessor and manipulation
    //! assert_eq!(dt.offset().fix().local_minus_utc(), 9 * 3600);
    //! assert_eq!(dt.timezone(), FixedOffset::east(9 * 3600));
    //! assert_eq!(dt.with_timezone(&Utc), Utc.ymd(2014, 11, 28).and_hms_nano(12, 45, 59, 324310806));
    //!
    //! // a sample of property manipulations (validates dynamically)
    //! assert_eq!(dt.with_day(29).unwrap().weekday(), Weekday::Sat); // 2014-11-29 is Saturday
    //! assert_eq!(dt.with_day(32), None);
    //! assert_eq!(dt.with_year(-300).unwrap().num_days_from_ce(), -109606); // November 29, 301 BCE
    //!
    //! // arithmetic operations
    //! let dt1 = Utc.ymd(2014, 11, 14).and_hms(8, 9, 10);
    //! let dt2 = Utc.ymd(2014, 11, 14).and_hms(10, 9, 8);
    //! assert_eq!(dt1.signed_duration_since(dt2), Duration::seconds(-2 * 3600 + 2));
    //! assert_eq!(dt2.signed_duration_since(dt1), Duration::seconds(2 * 3600 - 2));
    //! assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) + Duration::seconds(1_000_000_000),
    //!            Utc.ymd(2001, 9, 9).and_hms(1, 46, 40));
    //! assert_eq!(Utc.ymd(1970, 1, 1).and_hms(0, 0, 0) - Duration::seconds(1_000_000_000),
    //!            Utc.ymd(1938, 4, 24).and_hms(22, 13, 20));
    //! # }
    //! ```
    //!
    //! ### Formatting and Parsing
    //!
    //! Formatting is done via the [`format`](./struct.DateTime.html#method.format) method,
    //! which format is equivalent to the familiar `strftime` format.
    //!
    //! See [`format::strftime`](./format/strftime/index.html#specifiers)
    //! documentation for full syntax and list of specifiers.
    //!
    //! The default `to_string` method and `{:?}` specifier also give a reasonable representation.
    //! Chrono also provides [`to_rfc2822`](./struct.DateTime.html#method.to_rfc2822) and
    //! [`to_rfc3339`](./struct.DateTime.html#method.to_rfc3339) methods
    //! for well-known formats.
    //!
    //! Chrono now also provides date formatting in almost any language without the
    //! help of an additional C library. This functionality is under the feature
    //! `unstable-locales`:
    //!
    //! ```text
    //! chrono { version = "0.4", features = ["unstable-locales"]
    //! ```
    //!
    //! The `unstable-locales` feature requires and implies at least the `alloc` feature.
    //!
    //! ```rust
    //! use chrono::prelude::*;
    //!
    //! let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
    //! assert_eq!(dt.format("%Y-%m-%d %H:%M:%S").to_string(), "2014-11-28 12:00:09");
    //! assert_eq!(dt.format("%a %b %e %T %Y").to_string(), "Fri Nov 28 12:00:09 2014");
    //! assert_eq!(dt.format_localized("%A %e %B %Y, %T", Locale::fr_BE).to_string(), "vendredi 28 novembre 2014, 12:00:09");
    //! assert_eq!(dt.format("%a %b %e %T %Y").to_string(), dt.format("%c").to_string());
    //!
    //! assert_eq!(dt.to_string(), "2014-11-28 12:00:09 UTC");
    //! assert_eq!(dt.to_rfc2822(), "Fri, 28 Nov 2014 12:00:09 +0000");
    //! assert_eq!(dt.to_rfc3339(), "2014-11-28T12:00:09+00:00");
    //! assert_eq!(format!("{:?}", dt), "2014-11-28T12:00:09Z");
    //!
    //! // Note that milli/nanoseconds are only printed if they are non-zero
    //! let dt_nano = Utc.ymd(2014, 11, 28).and_hms_nano(12, 0, 9, 1);
    //! assert_eq!(format!("{:?}", dt_nano), "2014-11-28T12:00:09.000000001Z");
    //! ```
    //!
    //! Parsing can be done with three methods:
    //!
    //! 1. The standard [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html) trait
    //!    (and [`parse`](https://doc.rust-lang.org/std/primitive.str.html#method.parse) method
    //!    on a string) can be used for parsing `DateTime<FixedOffset>`, `DateTime<Utc>` and
    //!    `DateTime<Local>` values. This parses what the `{:?}`
    //!    ([`std::fmt::Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html))
    //!    format specifier prints, and requires the offset to be present.
    //!
    //! 2. [`DateTime::parse_from_str`](./struct.DateTime.html#method.parse_from_str) parses
    //!    a date and time with offsets and returns `DateTime<FixedOffset>`.
    //!    This should be used when the offset is a part of input and the caller cannot guess that.
    //!    It *cannot* be used when the offset can be missing.
    //!    [`DateTime::parse_from_rfc2822`](./struct.DateTime.html#method.parse_from_rfc2822)
    //!    and
    //!    [`DateTime::parse_from_rfc3339`](./struct.DateTime.html#method.parse_from_rfc3339)
    //!    are similar but for well-known formats.
    //!
    //! 3. [`Offset::datetime_from_str`](./offset/trait.TimeZone.html#method.datetime_from_str) is
    //!    similar but returns `DateTime` of given offset.
    //!    When the explicit offset is missing from the input, it simply uses given offset.
    //!    It issues an error when the input contains an explicit offset different
    //!    from the current offset.
    //!
    //! More detailed control over the parsing process is available via
    //! [`format`](./format/index.html) module.
    //!
    //! ```rust
    //! use chrono::prelude::*;
    //!
    //! let dt = Utc.ymd(2014, 11, 28).and_hms(12, 0, 9);
    //! let fixed_dt = dt.with_timezone(&FixedOffset::east(9*3600));
    //!
    //! // method 1
    //! assert_eq!("2014-11-28T12:00:09Z".parse::<DateTime<Utc>>(), Ok(dt.clone()));
    //! assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<Utc>>(), Ok(dt.clone()));
    //! assert_eq!("2014-11-28T21:00:09+09:00".parse::<DateTime<FixedOffset>>(), Ok(fixed_dt.clone()));
    //!
    //! // method 2
    //! assert_eq!(DateTime::parse_from_str("2014-11-28 21:00:09 +09:00", "%Y-%m-%d %H:%M:%S %z"),
    //!            Ok(fixed_dt.clone()));
    //! assert_eq!(DateTime::parse_from_rfc2822("Fri, 28 Nov 2014 21:00:09 +0900"),
    //!            Ok(fixed_dt.clone()));
    //! assert_eq!(DateTime::parse_from_rfc3339("2014-11-28T21:00:09+09:00"), Ok(fixed_dt.clone()));
    //!
    //! // method 3
    //! assert_eq!(Utc.datetime_from_str("2014-11-28 12:00:09", "%Y-%m-%d %H:%M:%S"), Ok(dt.clone()));
    //! assert_eq!(Utc.datetime_from_str("Fri Nov 28 12:00:09 2014", "%a %b %e %T %Y"), Ok(dt.clone()));
    //!
    //! // oops, the year is missing!
    //! assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T %Y").is_err());
    //! // oops, the format string does not include the year at all!
    //! assert!(Utc.datetime_from_str("Fri Nov 28 12:00:09", "%a %b %e %T").is_err());
    //! // oops, the weekday is incorrect!
    //! assert!(Utc.datetime_from_str("Sat Nov 28 12:00:09 2014", "%a %b %e %T %Y").is_err());
    //! ```
    //!
    //! Again : See [`format::strftime`](./format/strftime/index.html#specifiers)
    //! documentation for full syntax and list of specifiers.
    //!
    //! ### Conversion from and to EPOCH timestamps
    //!
    //! Use [`Utc.timestamp(seconds, nanoseconds)`](./offset/trait.TimeZone.html#method.timestamp)
    //! to construct a [`DateTime<Utc>`](./struct.DateTime.html) from a UNIX timestamp
    //! (seconds, nanoseconds that passed since January 1st 1970).
    //!
    //! Use [`DateTime.timestamp`](./struct.DateTime.html#method.timestamp) to get the timestamp (in seconds)
    //! from a [`DateTime`](./struct.DateTime.html). Additionally, you can use
    //! [`DateTime.timestamp_subsec_nanos`](./struct.DateTime.html#method.timestamp_subsec_nanos)
    //! to get the number of additional number of nanoseconds.
    //!
    //! ```rust
    //! // We need the trait in scope to use Utc::timestamp().
    //! use chrono::{DateTime, TimeZone, Utc};
    //!
    //! // Construct a datetime from epoch:
    //! let dt = Utc.timestamp(1_500_000_000, 0);
    //! assert_eq!(dt.to_rfc2822(), "Fri, 14 Jul 2017 02:40:00 +0000");
    //!
    //! // Get epoch value from a datetime:
    //! let dt = DateTime::parse_from_rfc2822("Fri, 14 Jul 2017 02:40:00 +0000").unwrap();
    //! assert_eq!(dt.timestamp(), 1_500_000_000);
    //! ```
    //!
    //! ### Individual date
    //!
    //! Chrono also provides an individual date type ([**`Date`**](./struct.Date.html)).
    //! It also has time zones attached, and have to be constructed via time zones.
    //! Most operations available to `DateTime` are also available to `Date` whenever appropriate.
    //!
    //! ```rust
    //! use chrono::prelude::*;
    //! use chrono::offset::LocalResult;
    //!
    //! # // these *may* fail, but only very rarely. just rerun the test if you were that unfortunate ;)
    //! assert_eq!(Utc::today(), Utc::now().date());
    //! assert_eq!(Local::today(), Local::now().date());
    //!
    //! assert_eq!(Utc.ymd(2014, 11, 28).weekday(), Weekday::Fri);
    //! assert_eq!(Utc.ymd_opt(2014, 11, 31), LocalResult::None);
    //! assert_eq!(Utc.ymd(2014, 11, 28).and_hms_milli(7, 8, 9, 10).format("%H%M%S").to_string(),
    //!            "070809");
    //! ```
    //!
    //! There is no timezone-aware `Time` due to the lack of usefulness and also the complexity.
    //!
    //! `DateTime` has [`date`](./struct.DateTime.html#method.date) method
    //! which returns a `Date` which represents its date component.
    //! There is also a [`time`](./struct.DateTime.html#method.time) method,
    //! which simply returns a naive local time described below.
    //!
    //! ### Naive date and time
    //!
    //! Chrono provides naive counterparts to `Date`, (non-existent) `Time` and `DateTime`
    //! as [**`NaiveDate`**](./naive/struct.NaiveDate.html),
    //! [**`NaiveTime`**](./naive/struct.NaiveTime.html) and
    //! [**`NaiveDateTime`**](./naive/struct.NaiveDateTime.html) respectively.
    //!
    //! They have almost equivalent interfaces as their timezone-aware twins,
    //! but are not associated to time zones obviously and can be quite low-level.
    //! They are mostly useful for building blocks for higher-level types.
    //!
    //! Timezone-aware `DateTime` and `Date` types have two methods returning naive versions:
    //! [`naive_local`](./struct.DateTime.html#method.naive_local) returns
    //! a view to the naive local time,
    //! and [`naive_utc`](./struct.DateTime.html#method.naive_utc) returns
    //! a view to the naive UTC time.
    //!
    //! ## Limitations
    //!
    //! Only proleptic Gregorian calendar (i.e. extended to support older dates) is supported.
    //! Be very careful if you really have to deal with pre-20C dates, they can be in Julian or others.
    //!
    //! Date types are limited in about +/- 262,000 years from the common epoch.
    //! Time types are limited in the nanosecond accuracy.
    //!
    //! [Leap seconds are supported in the representation but
    //! Chrono doesn't try to make use of them](./naive/struct.NaiveTime.html#leap-second-handling).
    //! (The main reason is that leap seconds are not really predictable.)
    //! Almost *every* operation over the possible leap seconds will ignore them.
    //! Consider using `NaiveDateTime` with the implicit TAI (International Atomic Time) scale
    //! if you want.
    //!
    //! Chrono inherently does not support an inaccurate or partial date and time representation.
    //! Any operation that can be ambiguous will return `None` in such cases.
    //! For example, "a month later" of 2014-01-30 is not well-defined
    //! and consequently `Utc.ymd(2014, 1, 30).with_month(2)` returns `None`.
    //!
    //! Non ISO week handling is not yet supported.
    //! For now you can use the [chrono_ext](https://crates.io/crates/chrono_ext)
    //! crate ([sources](https://github.com/bcourtine/chrono-ext/)).
    //!
    //! Advanced time zone handling is not yet supported.
    //! For now you can try the [Chrono-tz](https://github.com/chronotope/chrono-tz/) crate instead.

    #![doc(html_root_url = "https://docs.rs/chrono/latest/")]
    #![cfg_attr(feature = "bench", feature(test))] // lib stability features as per RFC #507
    #![deny(missing_docs)]
    #![deny(missing_debug_implementations)]
    #![deny(dead_code)]
    // lints are added all the time, we test on 1.13
    #![allow(unknown_lints)]
    #![cfg_attr(not(any(feature = "std", test)), no_std)]
    #![cfg_attr(feature = "cargo-clippy", allow(
        renamed_and_removed_lints,
        // The explicit 'static lifetimes are still needed for rustc 1.13-16
        // backward compatibility, and this appeases clippy. If minimum rustc
        // becomes 1.17, should be able to remove this, those 'static lifetimes,
        // and use `static` in a lot of places `const` is used now.
        redundant_static_lifetimes,
        // Similarly, redundant_field_names lints on not using the
        // field-init-shorthand, which was stabilized in rust 1.17.
        redundant_field_names,
        // Changing trivially_copy_pass_by_ref would require an incompatible version
        // bump.
        trivially_copy_pass_by_ref,
        try_err,
        // Currently deprecated, we use the separate implementation to add docs
        // warning that putting a time in a hash table is probably a bad idea
        derive_hash_xor_eq,
    ))]

    #[cfg(feature = "alloc")]
    extern crate alloc;
    #[cfg(all(feature = "std", not(feature = "alloc")))]
    extern crate std as alloc;
    #[cfg(any(feature = "std", test))]
    extern crate std as core;

    #[cfg(feature = "oldtime")]
    extern crate time as oldtime;
    #[cfg(not(feature = "oldtime"))]
    mod oldtime;

    #[cfg(feature = "clock")]
    extern crate libc;
    #[cfg(all(feature = "clock", windows))]
    extern crate winapi;
    #[cfg(all(
        feature = "clock",
        not(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))
    ))]
    mod sys;

    extern crate num_integer;
    extern crate num_traits;
    #[cfg(feature = "rustc-serialize")]
    extern crate rustc_serialize;
    #[cfg(feature = "serde")]
    extern crate serde as serdelib;
    #[cfg(feature = "__doctest")]
    #[cfg_attr(feature = "__doctest", cfg(doctest))]
    #[macro_use]
    extern crate doc_comment;
    #[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
    extern crate js_sys;
    #[cfg(feature = "unstable-locales")]
    extern crate pure_rust_locales;
    #[cfg(feature = "bench")]
    extern crate test;
    #[cfg(all(target_arch = "wasm32", not(target_os = "wasi"), feature = "wasmbind"))]
    extern crate wasm_bindgen;

    #[cfg(feature = "__doctest")]
    #[cfg_attr(feature = "__doctest", cfg(doctest))]
    doctest!("../README.md");

    // this reexport is to aid the transition and should not be in the prelude!
    pub use oldtime::Duration;

    pub use date::{Date, MAX_DATE, MIN_DATE};
    #[cfg(feature = "rustc-serialize")]
    pub use datetime::rustc_serialize::TsSeconds;
    pub use datetime::{DateTime, SecondsFormat, MAX_DATETIME, MIN_DATETIME};
    /// L10n locales.
    #[cfg(feature = "unstable-locales")]
    pub use format::Locale;
    pub use format::{ParseError, ParseResult};
    #[doc(no_inline)]
    pub use naive::{IsoWeek, NaiveDate, NaiveDateTime, NaiveTime};
    #[cfg(feature = "clock")]
    #[doc(no_inline)]
    pub use offset::Local;
    #[doc(no_inline)]
    pub use offset::{FixedOffset, LocalResult, Offset, TimeZone, Utc};
    pub use round::{DurationRound, RoundingError, SubsecRound};

    /// A convenience module appropriate for glob imports (`use chrono::prelude::*;`).
    pub mod prelude {
        #[doc(no_inline)]
        pub use Date;
        #[cfg(feature = "clock")]
        #[doc(no_inline)]
        pub use Local;
        #[cfg(feature = "unstable-locales")]
        #[doc(no_inline)]
        pub use Locale;
        #[doc(no_inline)]
        pub use SubsecRound;
        #[doc(no_inline)]
        pub use {DateTime, SecondsFormat};
        #[doc(no_inline)]
        pub use {Datelike, Month, Timelike, Weekday};
        #[doc(no_inline)]
        pub use {FixedOffset, Utc};
        #[doc(no_inline)]
        pub use {NaiveDate, NaiveDateTime, NaiveTime};
        #[doc(no_inline)]
        pub use {Offset, TimeZone};
    }

    // useful throughout the codebase
    macro_rules! try_opt {
        ($e:expr) => {
            match $e {
                Some(v) => v,
                None => return None,
            }
        };
    }

    mod div;
    pub mod offset;
    pub mod naive {
        //! Date and time types unconcerned with timezones.
        //!
        //! They are primarily building blocks for other types
        //! (e.g. [`TimeZone`](../offset/trait.TimeZone.html)),
        //! but can be also used for the simpler date and time handling.

        mod date;
        mod datetime;
        mod internals;
        mod isoweek;
        mod time;

        pub use self::date::{NaiveDate, MAX_DATE, MIN_DATE};
        #[cfg(feature = "rustc-serialize")]
        #[allow(deprecated)]
        pub use self::datetime::rustc_serialize::TsSeconds;
        pub use self::datetime::{NaiveDateTime, MAX_DATETIME, MIN_DATETIME};
        pub use self::isoweek::IsoWeek;
        pub use self::time::NaiveTime;

        #[cfg(feature = "__internal_bench")]
        #[doc(hidden)]
        pub use self::internals::YearFlags as __BenchYearFlags;

        /// Serialization/Deserialization of naive types in alternate formats
        ///
        /// The various modules in here are intended to be used with serde's [`with`
        /// annotation][1] to serialize as something other than the default [RFC
        /// 3339][2] format.
        ///
        /// [1]: https://serde.rs/attributes.html#field-attributes
        /// [2]: https://tools.ietf.org/html/rfc3339
        #[cfg(feature = "serde")]
        pub mod serde {
            pub use super::datetime::serde::*;
        }
    }
    mod date;
    mod datetime;
    pub mod format;
    mod round;

    #[cfg(feature = "__internal_bench")]
    #[doc(hidden)]
    pub use naive::__BenchYearFlags;

    /// Serialization/Deserialization in alternate formats
    ///
    /// The various modules in here are intended to be used with serde's [`with`
    /// annotation][1] to serialize as something other than the default [RFC
    /// 3339][2] format.
    ///
    /// [1]: https://serde.rs/attributes.html#field-attributes
    /// [2]: https://tools.ietf.org/html/rfc3339
    #[cfg(feature = "serde")]
    pub mod serde {
        pub use super::datetime::serde::*;
    }

    // Until rust 1.18 there  is no "pub(crate)" so to share this we need it in the root

    #[cfg(feature = "serde")]
    enum SerdeError<V: fmt::Display, D: fmt::Display> {
        NonExistent { timestamp: V },
        Ambiguous { timestamp: V, min: D, max: D },
    }

    /// Construct a [`SerdeError::NonExistent`]
    #[cfg(feature = "serde")]
    fn ne_timestamp<T: fmt::Display>(ts: T) -> SerdeError<T, u8> {
        SerdeError::NonExistent::<T, u8> { timestamp: ts }
    }

    #[cfg(feature = "serde")]
    impl<V: fmt::Display, D: fmt::Display> fmt::Debug for SerdeError<V, D> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "ChronoSerdeError({})", self)
        }
    }

    // impl<V: fmt::Display, D: fmt::Debug> core::error::Error for SerdeError<V, D> {}
    #[cfg(feature = "serde")]
    impl<V: fmt::Display, D: fmt::Display> fmt::Display for SerdeError<V, D> {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            match self {
                &SerdeError::NonExistent { ref timestamp } => {
                    write!(f, "value is not a legal timestamp: {}", timestamp)
                }
                &SerdeError::Ambiguous { ref timestamp, ref min, ref max } => write!(
                    f,
                    "value is an ambiguous timestamp: {}, could be either of {}, {}",
                    timestamp, min, max
                ),
            }
        }
    }

    /// The day of week.
    ///
    /// The order of the days of week depends on the context.
    /// (This is why this type does *not* implement `PartialOrd` or `Ord` traits.)
    /// One should prefer `*_from_monday` or `*_from_sunday` methods to get the correct result.
    #[derive(PartialEq, Eq, Copy, Clone, Debug, Hash)]
    #[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
    pub enum Weekday {
        /// Monday.
        Mon = 0,
        /// Tuesday.
        Tue = 1,
        /// Wednesday.
        Wed = 2,
        /// Thursday.
        Thu = 3,
        /// Friday.
        Fri = 4,
        /// Saturday.
        Sat = 5,
        /// Sunday.
        Sun = 6,
    }

    impl Weekday {
        /// The next day in the week.
        ///
        /// `w`:        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// ----------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.succ()`: | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun` | `Mon`
        #[inline]
        pub fn succ(&self) -> Weekday {
            match *self {
                Weekday::Mon => Weekday::Tue,
                Weekday::Tue => Weekday::Wed,
                Weekday::Wed => Weekday::Thu,
                Weekday::Thu => Weekday::Fri,
                Weekday::Fri => Weekday::Sat,
                Weekday::Sat => Weekday::Sun,
                Weekday::Sun => Weekday::Mon,
            }
        }

        /// The previous day in the week.
        ///
        /// `w`:        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// ----------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.pred()`: | `Sun` | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat`
        #[inline]
        pub fn pred(&self) -> Weekday {
            match *self {
                Weekday::Mon => Weekday::Sun,
                Weekday::Tue => Weekday::Mon,
                Weekday::Wed => Weekday::Tue,
                Weekday::Thu => Weekday::Wed,
                Weekday::Fri => Weekday::Thu,
                Weekday::Sat => Weekday::Fri,
                Weekday::Sun => Weekday::Sat,
            }
        }

        /// Returns a day-of-week number starting from Monday = 1. (ISO 8601 weekday number)
        ///
        /// `w`:                      | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// ------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.number_from_monday()`: | 1     | 2     | 3     | 4     | 5     | 6     | 7
        #[inline]
        pub fn number_from_monday(&self) -> u32 {
            match *self {
                Weekday::Mon => 1,
                Weekday::Tue => 2,
                Weekday::Wed => 3,
                Weekday::Thu => 4,
                Weekday::Fri => 5,
                Weekday::Sat => 6,
                Weekday::Sun => 7,
            }
        }

        /// Returns a day-of-week number starting from Sunday = 1.
        ///
        /// `w`:                      | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// ------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.number_from_sunday()`: | 2     | 3     | 4     | 5     | 6     | 7     | 1
        #[inline]
        pub fn number_from_sunday(&self) -> u32 {
            match *self {
                Weekday::Mon => 2,
                Weekday::Tue => 3,
                Weekday::Wed => 4,
                Weekday::Thu => 5,
                Weekday::Fri => 6,
                Weekday::Sat => 7,
                Weekday::Sun => 1,
            }
        }

        /// Returns a day-of-week number starting from Monday = 0.
        ///
        /// `w`:                        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// --------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.num_days_from_monday()`: | 0     | 1     | 2     | 3     | 4     | 5     | 6
        #[inline]
        pub fn num_days_from_monday(&self) -> u32 {
            match *self {
                Weekday::Mon => 0,
                Weekday::Tue => 1,
                Weekday::Wed => 2,
                Weekday::Thu => 3,
                Weekday::Fri => 4,
                Weekday::Sat => 5,
                Weekday::Sun => 6,
            }
        }

        /// Returns a day-of-week number starting from Sunday = 0.
        ///
        /// `w`:                        | `Mon` | `Tue` | `Wed` | `Thu` | `Fri` | `Sat` | `Sun`
        /// --------------------------- | ----- | ----- | ----- | ----- | ----- | ----- | -----
        /// `w.num_days_from_sunday()`: | 1     | 2     | 3     | 4     | 5     | 6     | 0
        #[inline]
        pub fn num_days_from_sunday(&self) -> u32 {
            match *self {
                Weekday::Mon => 1,
                Weekday::Tue => 2,
                Weekday::Wed => 3,
                Weekday::Thu => 4,
                Weekday::Fri => 5,
                Weekday::Sat => 6,
                Weekday::Sun => 0,
            }
        }
    }

    impl fmt::Display for Weekday {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            f.write_str(match *self {
                Weekday::Mon => "Mon",
                Weekday::Tue => "Tue",
                Weekday::Wed => "Wed",
                Weekday::Thu => "Thu",
                Weekday::Fri => "Fri",
                Weekday::Sat => "Sat",
                Weekday::Sun => "Sun",
            })
        }
    }

    /// Any weekday can be represented as an integer from 0 to 6, which equals to
    /// [`Weekday::num_days_from_monday`](#method.num_days_from_monday) in this implementation.
    /// Do not heavily depend on this though; use explicit methods whenever possible.
    impl num_traits::FromPrimitive for Weekday {
        #[inline]
        fn from_i64(n: i64) -> Option<Weekday> {
            match n {
                0 => Some(Weekday::Mon),
                1 => Some(Weekday::Tue),
                2 => Some(Weekday::Wed),
                3 => Some(Weekday::Thu),
                4 => Some(Weekday::Fri),
                5 => Some(Weekday::Sat),
                6 => Some(Weekday::Sun),
                _ => None,
            }
        }

        #[inline]
        fn from_u64(n: u64) -> Option<Weekday> {
            match n {
                0 => Some(Weekday::Mon),
                1 => Some(Weekday::Tue),
                2 => Some(Weekday::Wed),
                3 => Some(Weekday::Thu),
                4 => Some(Weekday::Fri),
                5 => Some(Weekday::Sat),
                6 => Some(Weekday::Sun),
                _ => None,
            }
        }
    }

    use core::fmt;

    /// An error resulting from reading `Weekday` value with `FromStr`.
    #[derive(Clone, PartialEq)]
    pub struct ParseWeekdayError {
        _dummy: (),
    }

    impl fmt::Debug for ParseWeekdayError {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "ParseWeekdayError {{ .. }}")
        }
    }

    // the actual `FromStr` implementation is in the `format` module to leverage the existing code

    #[cfg(feature = "serde")]
    mod weekday_serde {
        use super::Weekday;
        use core::fmt;
        use serdelib::{de, ser};

        impl ser::Serialize for Weekday {
            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
            where
                S: ser::Serializer,
            {
                serializer.collect_str(&self)
            }
        }

        struct WeekdayVisitor;

        impl<'de> de::Visitor<'de> for WeekdayVisitor {
            type Value = Weekday;

            fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
                write!(f, "Weekday")
            }

            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
            where
                E: de::Error,
            {
                value.parse().map_err(|_| E::custom("short or long weekday names expected"))
            }
        }

        impl<'de> de::Deserialize<'de> for Weekday {
            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
            where
                D: de::Deserializer<'de>,
            {
                deserializer.deserialize_str(WeekdayVisitor)
            }
        }

        #[cfg(test)]
        extern crate serde_json;

        #[test]
        fn test_serde_serialize() {
            use self::serde_json::to_string;
            use Weekday::*;

            let cases: Vec<(Weekday, &str)> = vec![
                (Mon, "\"Mon\""),
                (Tue, "\"Tue\""),
                (Wed, "\"Wed\""),
                (Thu, "\"Thu\""),
                (Fri, "\"Fri\""),
                (Sat, "\"Sat\""),
                (Sun, "\"Sun\""),
            ];

            for (weekday, expected_str) in cases {
                let string = to_string(&weekday).unwrap();
                assert_eq!(string, expected_str);
            }
        }

        #[test]
        fn test_serde_deserialize() {
            use self::serde_json::from_str;
            use Weekday::*;

            let cases: Vec<(&str, Weekday)> = vec![
                ("\"mon\"", Mon),
                ("\"MONDAY\"", Mon),
                ("\"MonDay\"", Mon),
                ("\"mOn\"", Mon),
                ("\"tue\"", Tue),
                ("\"tuesday\"", Tue),
                ("\"wed\"", Wed),
                ("\"wednesday\"", Wed),
                ("\"thu\"", Thu),
                ("\"thursday\"", Thu),
                ("\"fri\"", Fri),
                ("\"friday\"", Fri),
                ("\"sat\"", Sat),
                ("\"saturday\"", Sat),
                ("\"sun\"", Sun),
                ("\"sunday\"", Sun),
            ];

            for (str, expected_weekday) in cases {
                let weekday = from_str::<Weekday>(str).unwrap();
                assert_eq!(weekday, expected_weekday);
            }

            let errors: Vec<&str> =
                vec!["\"not a weekday\"", "\"monDAYs\"", "\"mond\"", "mon", "\"thur\"", "\"thurs\""];

            for str in errors {
                from_str::<Weekday>(str).unwrap_err();
            }
        }
    }

    /// The month of the year.
    ///
    /// This enum is just a convenience implementation.
    /// The month in dates created by DateLike objects does not return this enum.
    ///
    /// It is possible to convert from a date to a month independently
    /// ```
    /// # extern crate num_traits;
    /// use num_traits::FromPrimitive;
    /// use chrono::prelude::*;
    /// let date = Utc.ymd(2019, 10, 28).and_hms(9, 10, 11);
    /// // `2019-10-28T09:10:11Z`
    /// let month = Month::from_u32(date.month());
    /// assert_eq!(month, Some(Month::October))
    /// ```
    /// Or from a Month to an integer usable by dates
    /// ```
    /// # use chrono::prelude::*;
    /// let month = Month::January;
    /// let dt = Utc.ymd(2019, month.number_from_month(), 28).and_hms(9, 10, 11);
    /// assert_eq!((dt.year(), dt.month(), dt.day()), (2019, 1, 28));
    /// ```
    /// Allows mapping from and to month, from 1-January to 12-December.
    /// Can be Serialized/Deserialized with serde
    // Actual implementation is zero-indexed, API intended as 1-indexed for more intuitive behavior.
    #[derive(PartialEq, Eq, Copy, Clone, Debug, Hash)]
    #[cfg_attr(feature = "rustc-serialize", derive(RustcEncodable, RustcDecodable))]
    pub enum Month {
        /// January
        January = 0,
        /// February
        February = 1,
        /// March
        March = 2,
        /// April
        April = 3,
        /// May
        May = 4,
        /// June
        June = 5,
        /// July
        July = 6,
        /// August
        August = 7,
        /// September
        September = 8,
        /// October
        October = 9,
        /// November
        November = 10,
        /// December
        December = 11,
    }

    impl Month {
        /// The next month.
        ///
        /// `m`:        | `January`  | `February` | `...` | `December`
        /// ----------- | ---------  | ---------- | --- | ---------
        /// `m.succ()`: | `February` | `March`    | `...` | `January`
        #[inline]
        pub fn succ(&self) -> Month {
            match *self {
                Month::January => Month::February,
                Month::February => Month::March,
                Month::March => Month::April,
                Month::April => Month::May,
                Month::May => Month::June,
                Month::June => Month::July,
                Month::July => Month::August,
                Month::August => Month::September,
                Month::September => Month::October,
                Month::October => Month::November,
                Month::November => Month::December,
                Month::December => Month::January,
            }
        }

        /// The previous month.
        ///
        /// `m`:        | `January`  | `February` | `...` | `December`
        /// ----------- | ---------  | ---------- | --- | ---------
        /// `m.succ()`: | `December` | `January`  | `...` | `November`
        #[inline]
        pub fn pred(&self) -> Month {
            match *self {
                Month::January => Month::December,
                Month::February => Month::January,
                Month::March => Month::February,
                Month::April => Month::March,
                Month::May => Month::April,
                Month::June => Month::May,
                Month::July => Month::June,
                Month::August => Month::July,
                Month::September => Month::August,
                Month::October => Month::September,
                Month::November => Month::October,
                Month::December => Month::November,
            }
        }

        /// Returns a month-of-year number starting from January = 1.
        ///
        /// `m`:                     | `January` | `February` | `...` | `December`
        /// -------------------------| --------- | ---------- | --- | -----
        /// `m.number_from_month()`: | 1         | 2          | `...` | 12
        #[inline]
        pub fn number_from_month(&self) -> u32 {
            match *self {
                Month::January => 1,
                Month::February => 2,
                Month::March => 3,
                Month::April => 4,
                Month::May => 5,
                Month::June => 6,
                Month::July => 7,
                Month::August => 8,
                Month::September => 9,
                Month::October => 10,
                Month::November => 11,
                Month::December => 12,
            }
        }

        /// Get the name of the month
        ///
        /// ```
        /// use chrono::Month;
        ///
        /// assert_eq!(Month::January.name(), "January")
        /// ```
        pub fn name(&self) -> &'static str {
            match *self {
                Month::January => "January",
                Month::February => "February",
                Month::March => "March",
                Month::April => "April",
                Month::May => "May",
                Month::June => "June",
                Month::July => "July",
                Month::August => "August",
                Month::September => "September",
                Month::October => "October",
                Month::November => "November",
                Month::December => "December",
            }
        }
    }

    impl num_traits::FromPrimitive for Month {
        /// Returns an Option<Month> from a i64, assuming a 1-index, January = 1.
        ///
        /// `Month::from_i64(n: i64)`: | `1`                  | `2`                   | ... | `12`
        /// ---------------------------| -------------------- | --------------------- | ... | -----
        /// ``:                        | Some(Month::January) | Some(Month::February) | ... | Some(Month::December)

        #[inline]
        fn from_u64(n: u64) -> Option<Month> {
            Self::from_u32(n as u32)
        }

        #[inline]
        fn from_i64(n: i64) -> Option<Month> {
            Self::from_u32(n as u32)
        }

        #[inline]
        fn from_u32(n: u32) -> Option<Month> {
            match n {
                1 => Some(Month::January),
                2 => Some(Month::February),
                3 => Some(Month::March),
                4 => Some(Month::April),
                5 => Some(Month::May),
                6 => Some(Month::June),
                7 => Some(Month::July),
                8 => Some(Month::August),
                9 => Some(Month::September),
                10 => Some(Month::October),
                11 => Some(Month::November),
                12 => Some(Month::December),
                _ => None,
            }
        }
    }

    /// An error resulting from reading `<Month>` value with `FromStr`.
    #[derive(Clone, PartialEq)]
    pub struct ParseMonthError {
        _dummy: (),
    }

    impl fmt::Debug for ParseMonthError {
        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
            write!(f, "ParseMonthError {{ .. }}")
        }
    }

    #[cfg(feature = "serde")]
    mod month_serde {
        use super::Month;
        use serdelib::{de, ser};

        use core::fmt;

        impl ser::Serialize for Month {
            fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
            where
                S: ser::Serializer,
            {
                serializer.collect_str(self.name())
            }
        }

        struct MonthVisitor;

        impl<'de> de::Visitor<'de> for MonthVisitor {
            type Value = Month;

            fn expecting(&self, f: &mut fmt::Formatter) -> fmt::Result {
                write!(f, "Month")
            }

            fn visit_str<E>(self, value: &str) -> Result<Self::Value, E>
            where
                E: de::Error,
            {
                value.parse().map_err(|_| E::custom("short (3-letter) or full month names expected"))
            }
        }

        impl<'de> de::Deserialize<'de> for Month {
            fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
            where
                D: de::Deserializer<'de>,
            {
                deserializer.deserialize_str(MonthVisitor)
            }
        }

        #[cfg(test)]
        extern crate serde_json;

        #[test]
        fn test_serde_serialize() {
            use self::serde_json::to_string;
            use Month::*;

            let cases: Vec<(Month, &str)> = vec![
                (January, "\"January\""),
                (February, "\"February\""),
                (March, "\"March\""),
                (April, "\"April\""),
                (May, "\"May\""),
                (June, "\"June\""),
                (July, "\"July\""),
                (August, "\"August\""),
                (September, "\"September\""),
                (October, "\"October\""),
                (November, "\"November\""),
                (December, "\"December\""),
            ];

            for (month, expected_str) in cases {
                let string = to_string(&month).unwrap();
                assert_eq!(string, expected_str);
            }
        }

        #[test]
        fn test_serde_deserialize() {
            use self::serde_json::from_str;
            use Month::*;

            let cases: Vec<(&str, Month)> = vec![
                ("\"january\"", January),
                ("\"jan\"", January),
                ("\"FeB\"", February),
                ("\"MAR\"", March),
                ("\"mar\"", March),
                ("\"april\"", April),
                ("\"may\"", May),
                ("\"june\"", June),
                ("\"JULY\"", July),
                ("\"august\"", August),
                ("\"september\"", September),
                ("\"October\"", October),
                ("\"November\"", November),
                ("\"DECEmbEr\"", December),
            ];

            for (string, expected_month) in cases {
                let month = from_str::<Month>(string).unwrap();
                assert_eq!(month, expected_month);
            }

            let errors: Vec<&str> =
                vec!["\"not a month\"", "\"ja\"", "\"Dece\"", "Dec", "\"Augustin\""];

            for string in errors {
                from_str::<Month>(string).unwrap_err();
            }
        }
    }

    /// The common set of methods for date component.
    pub trait Datelike: Sized {
        /// Returns the year number in the [calendar date](./naive/struct.NaiveDate.html#calendar-date).
        fn year(&self) -> i32;

        /// Returns the absolute year number starting from 1 with a boolean flag,
        /// which is false when the year predates the epoch (BCE/BC) and true otherwise (CE/AD).
        #[inline]
        fn year_ce(&self) -> (bool, u32) {
            let year = self.year();
            if year < 1 {
                (false, (1 - year) as u32)
            } else {
                (true, year as u32)
            }
        }

        /// Returns the month number starting from 1.
        ///
        /// The return value ranges from 1 to 12.
        fn month(&self) -> u32;

        /// Returns the month number starting from 0.
        ///
        /// The return value ranges from 0 to 11.
        fn month0(&self) -> u32;

        /// Returns the day of month starting from 1.
        ///
        /// The return value ranges from 1 to 31. (The last day of month differs by months.)
        fn day(&self) -> u32;

        /// Returns the day of month starting from 0.
        ///
        /// The return value ranges from 0 to 30. (The last day of month differs by months.)
        fn day0(&self) -> u32;

        /// Returns the day of year starting from 1.
        ///
        /// The return value ranges from 1 to 366. (The last day of year differs by years.)
        fn ordinal(&self) -> u32;

        /// Returns the day of year starting from 0.
        ///
        /// The return value ranges from 0 to 365. (The last day of year differs by years.)
        fn ordinal0(&self) -> u32;

        /// Returns the day of week.
        fn weekday(&self) -> Weekday;

        /// Returns the ISO week.
        fn iso_week(&self) -> IsoWeek;

        /// Makes a new value with the year number changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_year(&self, year: i32) -> Option<Self>;

        /// Makes a new value with the month number (starting from 1) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_month(&self, month: u32) -> Option<Self>;

        /// Makes a new value with the month number (starting from 0) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_month0(&self, month0: u32) -> Option<Self>;

        /// Makes a new value with the day of month (starting from 1) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_day(&self, day: u32) -> Option<Self>;

        /// Makes a new value with the day of month (starting from 0) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_day0(&self, day0: u32) -> Option<Self>;

        /// Makes a new value with the day of year (starting from 1) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_ordinal(&self, ordinal: u32) -> Option<Self>;

        /// Makes a new value with the day of year (starting from 0) changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_ordinal0(&self, ordinal0: u32) -> Option<Self>;

        /// Counts the days in the proleptic Gregorian calendar, with January 1, Year 1 (CE) as day 1.
        ///
        /// # Examples
        ///
        /// ```
        /// use chrono::{NaiveDate, Datelike};
        ///
        /// assert_eq!(NaiveDate::from_ymd(1970, 1, 1).num_days_from_ce(), 719_163);
        /// assert_eq!(NaiveDate::from_ymd(2, 1, 1).num_days_from_ce(), 366);
        /// assert_eq!(NaiveDate::from_ymd(1, 1, 1).num_days_from_ce(), 1);
        /// assert_eq!(NaiveDate::from_ymd(0, 1, 1).num_days_from_ce(), -365);
        /// ```
        fn num_days_from_ce(&self) -> i32 {
            // See test_num_days_from_ce_against_alternative_impl below for a more straightforward
            // implementation.

            // we know this wouldn't overflow since year is limited to 1/2^13 of i32's full range.
            let mut year = self.year() - 1;
            let mut ndays = 0;
            if year < 0 {
                let excess = 1 + (-year) / 400;
                year += excess * 400;
                ndays -= excess * 146_097;
            }
            let div_100 = year / 100;
            ndays += ((year * 1461) >> 2) - div_100 + (div_100 >> 2);
            ndays + self.ordinal() as i32
        }
    }

    /// The common set of methods for time component.
    pub trait Timelike: Sized {
        /// Returns the hour number from 0 to 23.
        fn hour(&self) -> u32;

        /// Returns the hour number from 1 to 12 with a boolean flag,
        /// which is false for AM and true for PM.
        #[inline]
        fn hour12(&self) -> (bool, u32) {
            let hour = self.hour();
            let mut hour12 = hour % 12;
            if hour12 == 0 {
                hour12 = 12;
            }
            (hour >= 12, hour12)
        }

        /// Returns the minute number from 0 to 59.
        fn minute(&self) -> u32;

        /// Returns the second number from 0 to 59.
        fn second(&self) -> u32;

        /// Returns the number of nanoseconds since the whole non-leap second.
        /// The range from 1,000,000,000 to 1,999,999,999 represents
        /// the [leap second](./naive/struct.NaiveTime.html#leap-second-handling).
        fn nanosecond(&self) -> u32;

        /// Makes a new value with the hour number changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_hour(&self, hour: u32) -> Option<Self>;

        /// Makes a new value with the minute number changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        fn with_minute(&self, min: u32) -> Option<Self>;

        /// Makes a new value with the second number changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        /// As with the [`second`](#tymethod.second) method,
        /// the input range is restricted to 0 through 59.
        fn with_second(&self, sec: u32) -> Option<Self>;

        /// Makes a new value with nanoseconds since the whole non-leap second changed.
        ///
        /// Returns `None` when the resulting value would be invalid.
        /// As with the [`nanosecond`](#tymethod.nanosecond) method,
        /// the input range can exceed 1,000,000,000 for leap seconds.
        fn with_nanosecond(&self, nano: u32) -> Option<Self>;

        /// Returns the number of non-leap seconds past the last midnight.
        #[inline]
        fn num_seconds_from_midnight(&self) -> u32 {
            self.hour() * 3600 + self.minute() * 60 + self.second()
        }
    }

    #[cfg(test)]
    extern crate num_iter;

    mod test {
        #[allow(unused_imports)]
        use super::*;

        #[test]
        fn test_readme_doomsday() {
            use num_iter::range_inclusive;

            for y in range_inclusive(naive::MIN_DATE.year(), naive::MAX_DATE.year()) {
                // even months
                let d4 = NaiveDate::from_ymd(y, 4, 4);
                let d6 = NaiveDate::from_ymd(y, 6, 6);
                let d8 = NaiveDate::from_ymd(y, 8, 8);
                let d10 = NaiveDate::from_ymd(y, 10, 10);
                let d12 = NaiveDate::from_ymd(y, 12, 12);

                // nine to five, seven-eleven
                let d59 = NaiveDate::from_ymd(y, 5, 9);
                let d95 = NaiveDate::from_ymd(y, 9, 5);
                let d711 = NaiveDate::from_ymd(y, 7, 11);
                let d117 = NaiveDate::from_ymd(y, 11, 7);

                // "March 0"
                let d30 = NaiveDate::from_ymd(y, 3, 1).pred();

                let weekday = d30.weekday();
                let other_dates = [d4, d6, d8, d10, d12, d59, d95, d711, d117];
                assert!(other_dates.iter().all(|d| d.weekday() == weekday));
            }
        }

        #[test]
        fn test_month_enum_primitive_parse() {
            use num_traits::FromPrimitive;

            let jan_opt = Month::from_u32(1);
            let feb_opt = Month::from_u64(2);
            let dec_opt = Month::from_i64(12);
            let no_month = Month::from_u32(13);
            assert_eq!(jan_opt, Some(Month::January));
            assert_eq!(feb_opt, Some(Month::February));
            assert_eq!(dec_opt, Some(Month::December));
            assert_eq!(no_month, None);

            let date = Utc.ymd(2019, 10, 28).and_hms(9, 10, 11);
            assert_eq!(Month::from_u32(date.month()), Some(Month::October));

            let month = Month::January;
            let dt = Utc.ymd(2019, month.number_from_month(), 28).and_hms(9, 10, 11);
            assert_eq!((dt.year(), dt.month(), dt.day()), (2019, 1, 28));
        }
    }

    /// Tests `Datelike::num_days_from_ce` against an alternative implementation.
    ///
    /// The alternative implementation is not as short as the current one but it is simpler to
    /// understand, with less unexplained magic constants.
    #[test]
    fn test_num_days_from_ce_against_alternative_impl() {
        /// Returns the number of multiples of `div` in the range `start..end`.
        ///
        /// If the range `start..end` is back-to-front, i.e. `start` is greater than `end`, the
        /// behaviour is defined by the following equation:
        /// `in_between(start, end, div) == - in_between(end, start, div)`.
        ///
        /// When `div` is 1, this is equivalent to `end - start`, i.e. the length of `start..end`.
        ///
        /// # Panics
        ///
        /// Panics if `div` is not positive.
        fn in_between(start: i32, end: i32, div: i32) -> i32 {
            assert!(div > 0, "in_between: nonpositive div = {}", div);
            let start = (start.div_euclid(div), start.rem_euclid(div));
            let end = (end.div_euclid(div), end.rem_euclid(div));
            // The lowest multiple of `div` greater than or equal to `start`, divided.
            let start = start.0 + (start.1 != 0) as i32;
            // The lowest multiple of `div` greater than or equal to   `end`, divided.
            let end = end.0 + (end.1 != 0) as i32;
            end - start
        }

        /// Alternative implementation to `Datelike::num_days_from_ce`
        fn num_days_from_ce<Date: Datelike>(date: &Date) -> i32 {
            let year = date.year();
            let diff = move |div| in_between(1, year, div);
            // 365 days a year, one more in leap years. In the gregorian calendar, leap years are all
            // the multiples of 4 except multiples of 100 but including multiples of 400.
            date.ordinal() as i32 + 365 * diff(1) + diff(4) - diff(100) + diff(400)
        }

        use num_iter::range_inclusive;

        for year in range_inclusive(naive::MIN_DATE.year(), naive::MAX_DATE.year()) {
            let jan1_year = NaiveDate::from_ymd(year, 1, 1);
            assert_eq!(
                jan1_year.num_days_from_ce(),
                num_days_from_ce(&jan1_year),
                "on {:?}",
                jan1_year
            );
            let mid_year = jan1_year + Duration::days(133);
            assert_eq!(mid_year.num_days_from_ce(), num_days_from_ce(&mid_year), "on {:?}", mid_year);
        }
    }

    #[test]
    fn test_month_enum_succ_pred() {
        assert_eq!(Month::January.succ(), Month::February);
        assert_eq!(Month::December.succ(), Month::January);
        assert_eq!(Month::January.pred(), Month::December);
        assert_eq!(Month::February.pred(), Month::January);
    }