An implementation of the proleptic Gregorian calendar, compatible with ISO 8601. Amongst others, that means that the calendar has a year zero preceeding the year 1.
This create does not deal with times or time zones.
The [Date] type represents a date (year, month and day),
the [Year] type represents a calendar year,
the [Month] type represents a calendar month,
and the [YearMonth] type represents a month of a specific year.
Where possible, things are implemented as const fn.
Currently, this excludes trait implementations and functions that rely on traits.
```rust use gregorian::{Date, Month::*, Year, YearMonth};
assert!(Year::new(2020).hasleapday(), true); assert!(YearMonth::new(1900, February).totaldays() == 28); assert!(YearMonth::new(2000, February).totaldays() == 29);
assert!(Year::new(2020).withmonth(March).firstday() == Date::new(2020, March, 1).unwrap()); assert!(Year::new(2020).withmonth(March).lastday() == Date::new(2020, March, 31).unwrap());
assert!(Year::new(2020).firstday() == Date::new(2020, 1, 1).unwrap()); assert!(Year::new(2020).lastday() == Date::new(2020, 12, 31).unwrap());
assert!(Date::new(2020, 2, 1).unwrap().dayofyear() == 32); ```
When you use [Date::add_years()] or [Date::add_months()], you can get invalid dates.
These are reported with an [InvalidDayOfMonth] error which has the
next_valid() and prev_valid() methods.
Those can be used to get the next or previous valid date instead.
Additionally, there is an extension trait for Result<Date, InvalidDayOfMonth> with the
or_next_valid() and or_prev_valid() methods.
This allows you to directly round the date on the Result object.
rust
use gregorian::{Date, DateResultExt};
let date = Date::new(2020, 1, 31).unwrap();
assert!(date.add_months(1).or_next_valid() == Date::new(2020, 3, 1).unwrap());
assert!(date.add_months(1).or_prev_valid() == Date::new(2020, 2, 29).unwrap());