# speedate

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Fast and simple datetime, date, time and duration parsing for rust.

**speedate** is a lax† **RFC 3339** date and time parser, in other words, it parses common **ISO 8601**
formats.

**†** - all relaxations of from [RFC 3339](https://tools.ietf.org/html/rfc3339)
are compliant with [ISO 8601](https://en.wikipedia.org/wiki/ISO_8601).

The following formats are supported:
* Date: `YYYY-MM-DD`
* Time: `HH:MM:SS`
* Time: `HH:MM:SS.FFFFFF` 1 to 6 digits are reflected in the `time.microsecond`, extra digits are ignored
* Time: `HH:MM`
* Date time: `YYYY-MM-DDTHH:MM:SS` - all the above time formats are allowed for the time part
* Date time: `YYYY-MM-DD HH:MM:SS` - `T`, `t`, ` ` and `_` are allowed as separators
* Date time: `YYYY-MM-DDTHH:MM:SSZ` - `Z` or `z` is allowed as timezone
* Date time: `YYYY-MM-DDTHH:MM:SS+08:00`- positive and negative timezone are allowed, as per ISO 8601, U+2212 minus `−`
  is allowed as well as ascii minus `-` (U+002D)
* Date time: `YYYY-MM-DDTHH:MM:SS+0800` - the colon (`:`) in the timezone is optional
* Duration: `PnYnMnDTnHnMnS` - ISO 8601 duration format,
  see [wikipedia](https://en.wikipedia.org/wiki/ISO_8601#Durations) for more details, `W` for weeks is also allowed
* Duration: `HH:MM:SS` - any of the above time formats are allowed to represent a duration
* Duration: `D days, HH:MM:SS` - time prefixed by `X days`, case-insensitive, spaces `s` and `,` are all optional
* Duration: `D d, HH:MM:SS` - time prefixed by `X d`, case-insensitive, spaces and `,` are optional
* Duration: `±...` - all duration formats shown here can be prefixed with `+` or `-` to indicate
  positive and negative durations respectively

In addition, unix timestamps (both seconds and milliseconds) can be used to create dates and datetimes.

See [the documentation](https://docs.rs/speedate/latest/speedate/index.html#structs) for each struct for more details.

This will be the datetime parsing logic for [pydantic-core](https://github.com/pydantic/pydantic-core).

## Usage

```rust
use speedate::{DateTime, Date, Time};

let dt = DateTime::parse_str("2022-01-01T12:13:14Z").unwrap();
assert_eq!(
    dt,
    DateTime {
        date: Date {
            year: 2022,
            month: 1,
            day: 1,
        },
        time: Time {
            hour: 12,
            minute: 13,
            second: 14,
            microsecond: 0,
            tz_offset: Some(0),
        },
    }
);
assert_eq!(dt.to_string(), "2022-01-01T12:13:14Z");
```

To control the specifics of time parsing you can use provide a `TimeConfig`:

```rust
use speedate::{DateTime, Date, Time, TimeConfig, MicrosecondsPrecisionOverflowBehavior};
let dt = DateTime::parse_bytes_with_config(
    "1689102037.5586429".as_bytes(),
    &TimeConfig::builder()
        .unix_timestamp_offset(Some(0))
        .microseconds_precision_overflow_behavior(MicrosecondsPrecisionOverflowBehavior::Truncate)
        .build(),
).unwrap();
assert_eq!(
    dt,
    DateTime {
        date: Date {
            year: 2023,
            month: 7,
            day: 11,
        },
        time: Time {
            hour: 19,
            minute: 0,
            second: 37,
            microsecond: 558643,
            tz_offset: Some(0),
        },
    }
);
assert_eq!(dt.to_string(), "2023-07-11T19:00:37.558643Z");
```

## Performance

**speedate** is significantly faster than
[chrono's `parse_from_rfc3339`](https://docs.rs/chrono/latest/chrono/struct.DateTime.html#method.parse_from_rfc3339)
and [iso8601](https://crates.io/crates/iso8601).

Micro-benchmarking from [`benches/main.rs`](https://github.com/pydantic/speedate/blob/main/benches/main.rs):

```text
test datetime_error_speedate ... bench:           6 ns/iter (+/- 0)
test datetime_error_chrono   ... bench:          50 ns/iter (+/- 1)
test datetime_error_iso8601  ... bench:         118 ns/iter (+/- 2)
test datetime_ok_speedate    ... bench:           9 ns/iter (+/- 0)
test datetime_ok_chrono      ... bench:         182 ns/iter (+/- 0)
test datetime_ok_iso8601     ... bench:          77 ns/iter (+/- 1)
test duration_ok_speedate    ... bench:          23 ns/iter (+/- 0)
test duration_ok_iso8601     ... bench:          48 ns/iter (+/- 0)
test timestamp_ok_speedate   ... bench:           9 ns/iter (+/- 0)
test timestamp_ok_chrono     ... bench:          10 ns/iter (+/- 0)
```

## Why not full iso8601?

ISO8601 allows many formats, see
[ijmacd.github.io/rfc3339-iso8601](https://ijmacd.github.io/rfc3339-iso8601/).

Most of these are unknown to most users, and not desired. This library aims to support the most common formats
without introducing ambiguity.
