RESOLUTION A4
  
  ON THE MODIFICATION OF DATE VALUES ON FITS SOFTWARE


    The XXIIIrd International Astronomical Union General Assembly,

  Recognizing
        that the two-digit year numbers in the date values of keywords such as
        DATE-OBS='31/12/99' in FITS files will become ambiguous on the day 2000-01-01,

    and noting
         that the IAU FITS Working Group has adopted new rules for DATExxxx
	 value strings which specify that the previous convention applies only to 
	 dates in the range 1900-1999 and that the new convention DATE-OBS='1999-12-31'
	 is to be used in data interchange and in data archives beginning 1998-01-01,

    Urges all IAU members
              to ensure that their FITS writing and reading software is modified before
	      1998-01-01 to support both the new convention and the old convention, in
	      accordance with the rules specified by the IAU FITS Working Group..

Reference: Transactions of the International Astronomical Union (1997), Vol. XXIIIB, p. 35.