If x is a recognized date-time object, leap_year will return whether x occurs during a leap year. If x is a number, leap_year returns whether it would be a leap year under the Gregorian calendar.

## Examples

```
x <- as.Date("2009-08-02")
leap_year(x) # FALSE
#> [1] FALSE
leap_year(2009) # FALSE
#> [1] FALSE
leap_year(2008) # TRUE
#> [1] TRUE
leap_year(1900) # FALSE
#> [1] FALSE
leap_year(2000) # TRUE
#> [1] TRUE
```