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julian is a Rust library for converting between Julian day numbers and dates in the Gregorian calendar (either proleptic or with the Reformation occurring at a given date) and/or the proleptic Julian calendar. There are also features for querying details about years & months in a "reforming" Gregorian calendar and how they are affected by the calendar reformation date of your choice.

Examples

Before you construct a date, you must first choose a calendar in which to reckon dates. Calendar::GREGORIAN is the proleptic Gregorian calendar, which should be both simple and useful enough for most basic purposes.

To convert a Julian day number to a date in a calendar, use the Calendar::at_jdn() method, like so:

```rust use julian::{Calendar, Month};

let cal = Calendar::GREGORIAN; let date = cal.atjdn(2460065); asserteq!(date.year(), 2023); asserteq!(date.month(), Month::April); asserteq!(date.day(), 30); ```

So JDN 2460065 is April 30, 2023, in the proleptic Gregorian calendar.

To convert a date to a Julian day number, use Calendar::at_ymd() to construct the date, and then call its julian_day_number() method:

```rust use julian::{Calendar, Month};

let cal = Calendar::GREGORIAN; let date = cal.atymd(2023, Month::April, 30).unwrap(); asserteq!(date.juliandaynumber(), 2460065); ```

See the documentation for more things you can do!