!      call j1980mdy(j1980date,mo,iday,iyear) !convert daycount (1980 to..)
!      returns month=(1-12) day of month, and year.
!      j1980date is  # days from 1 1 1980 (1 1 1980 is returned for date=1)
	subroutine j1980mdy(nday,mon,day,iy)                             
	implicit none
	integer*4 i,nday,mon,day,iy,nn
        integer,save:: monlen(11)
	data monlen/31,28,31,30,31,30,31,31,30,31,30/
	day=nday                      	!safe to modify returned da of mo
	iy=1980                         !year 0 in this system
	do while (day.gt.0)     	!find year
	 nn=365                         !not a leap
	 if(mod(iy,4).eq.0) nn=366	!leap year 
	 if(mod(iy,100).eq.0) nn=365	!not leap year (2100)
	 if(mod(iy,400).eq.0) nn=366	!leap year (2000)
	 if(day.gt.nn)then
	  iy=iy+1        		!not done yet, add a year
	  day=day-nn                 	!account for days in year just added
	 else
	  goto 123
	 endif
 	enddo
	
123	monlen(2)=28
	if(mod(iy,4).eq.0) monlen(2)=29 	!leap year 
	if(mod(iy,100).eq.0) monlen(2)=28	!not leap year (2100)
	if(mod(iy,400).eq.0) monlen(2)=29	!leap year (2000)
	mon=1                           !init january
!
	do i=1,11                       !find month and day
	 if(day.gt.monlen(mon)) then	!another month to count
	  day=day-monlen(i)             !account for days
	  mon=mon+1                     !next month
	 endif
	enddo
	return
	end