Function `is_leap_year`

const fn is_leap_year(year: i32) -> bool

Returns if the provided year is a leap year in the proleptic Gregorian calendar. Uses astronomical year numbering.

# use time::util::is_leap_year;
assert!(!is_leap_year(1900));
assert!(is_leap_year(2000));
assert!(is_leap_year(2004));
assert!(!is_leap_year(2005));
assert!(!is_leap_year(2100));