;------------------------------------------------------------
;------------------------------------------------------------
;------------------------------------------------------------
;+
;
; @file_comments
; give the number of days in a specific month
;
; @categories calendar
;
; @param year {in}{optional}{default=from "time" common variable of cm_4cal}
; To specify the year of the onth. Used only if the common variable
; key_caltype = 'greg'. In that case, month and year must have the same
; number of elements.
;
; @returns 
; number of days in a month or -1 in case of error
;
; @uses cm_4cal, updatenew
;
; @examples
; IDL> ndays = daysinmonth(2, 2000)
;
; @history Sebastien Masson (smasson\@lodyc.jussieu.fr)
; 2/7/98
; update/review/english/new commons: June 2005 Sebastien Masson.
;
; @version $Id$
;
;-
;------------------------------------------------------------
;------------------------------------------------------------
;------------------------------------------------------------
function daysinmonth, month, year
;------------------------------------------------------------
; include commons
;
  compile_opt idl2, strictarrsubs
;
@cm_4cal
IF NOT keyword_set(key_forgetold) THEN BEGIN
@updatenew
ENDIF
;------------------------------------------------------------
  IF n_elements(key_caltype) EQ 0 THEN key_caltype = 'greg'
  CASE key_caltype OF
    '360d': if n_elements(month) GT 1 THEN $
        return, replicate(30, n_elements(month)) ELSE return, 30
    'noleap':BEGIN
      days_in_mth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
      IF n_elements(month) EQ 0 THEN caldat, time, month
      return, days_in_mth[month-1]
    END
    'greg':BEGIN
      CASE n_params() OF
        0:caldat, time, month, day, year
        2:IF n_elements(month) NE n_elements(year) THEN $
          return, report('month and year must have the same number of elements')
        ELSE:return, report('daysinmonth accept 0 or 2 input parameters')
      ENDCASE
      days_in_mth = [31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31]
      return, days_in_mth[month-1] + leapyr(year)*(month EQ 2)
    END
    ELSE:return, report('only 3 types of calendar are accepted: greg, 360d and noleap')
  ENDCASE

END