An implementation of the proleptic Gregorian calendar. In this implementation, before the year 1 come year 0. The library does not deal with times.
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.
```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); ```