;+ ; NAME: ; leap_year ; ; ; PURPOSE: ; compute if an array of years are leap years ; ; ; INPUTS: ; year: array of any size/shape of years ; (of course leap years are only valid ; over a range of AD dates past ~4AD) ; ; ; KEYWORD PARAMETERS: ; NUMDAYS: if set returns the number of days in the year instead of ; a login 1/0 ; ; ; OUTPUTS: ; array of logic 1/0 where 1 is leap year and zero is not ; ; ; EXAMPLE: ; IDL> print, leap_year(findgen(2,5)+1900) ; 0 0 ; 0 0 ; 1 0 ; 0 0 ; 1 0 ; ; IDL> print, leap_year(findgen(10)+1900) ; 0 0 0 0 1 0 0 0 1 0 ; ; ; ; MODIFICATION HISTORY: ; ; Thur Feb 8 16:37:16 2007, Brian Larsen ; written and tested ; ;- FUNCTION leap_year, year, NUMDAYS=numdays mask400 = year mod 400 EQ 0 ; this is a leap year mask100 = year mod 100 EQ 0 ; these are not leap years mask4 = year mod 4 EQ 0 ; this is a leap year if n_elements(numdays) eq 0 then $ numdays = 0 else $ numdays = 365 RETURN, numdays + ((mask400 or mask4) and (~mask100 or mask400)) END