idlastro / Astronomical Utilities: YDN2MD

[Source code]

NAME
YDN2MD
PURPOSE
Convert from year and day number of year to month and day of month.       
CALLING SEQUENCE
YDN2MD,yr,dy,m,d
INPUTS
yr = 4 digit year (like 1988), integer scalar
dy = day number in year (like 310), integer scalar or vector
OUTPUTS
m = month number (1-12, e.g. 11 = Nov)   
d = day of month (like 5).          
Note: On error returns m = d = -1.
EXAMPLE
Find the month/day of days 155 and 255 in the year 2001
IDL> ydn2md, 2001, [155,255], m, d
  ==> m = [6,9]   & d = [4,12]        ; = June 4 and September 12 
MODIFICATION HISTORY
Adapted from Johns Hopkins University/Applied Physics Laboratory
Update to use VALUE_LOCATE,   W. Landsman    January 2001