RPFITS Modification for the Year 2000 problem

RPFITS does not use the FITS standard date keywords because it specifies 
date as UT, not the standard UTC. For this reason the time system is
explicitly stated in comments.

The date keywords in RPFITS are these:
  DATOBS   char*8 dd/mm/yy  UT date of observation
  DATWRIT  char*8 dd/mm/yy  UT date of writing file
  DATSYS   char*8 dd/mm/yy  Date system, being AEST, UT
                            or blank (defaulting to UT)
  NX_DATE  char*8 dd/mm/yy  UT date of start of scan

The new date format sanctioned by IAU FITS Working Group has a short 
and a long form ie
  yyyy-mm-dd                     char*10
  yyyy-mm-ddThh:mm:ss[.sss...]   char*21 or longer

The short form will be used in RPFITS when this version is implemented
  . in all FITS files written
  . in common blocks when all FITS files are read.
Dates in either the old or new form will be accepted by both
RPFITSIN and RPFITSOUT.

The date keywords listed above as char*8 will all become char*10.

The Fortran library routine IDATE can no longer be used by RPFITSOUT to 
get the current date in the required form for DATWRIT. It returns a 
2 digit year. ie
  call idate(im, id, iy) with the -V77 option
  call idate(iarray(3)) without the -V77 option

Instead the Fortran library routine FDATE will be used. It returns
a 23 or 24 character string.
  eg     Mon Aug 1 09:24:21 1994
      or Mon Aug 15 09:24:21 1994
  
A subroutine will use FDATE to produce a date in the new format.
  character*8 old_date                if blank, uses the current date
  character*10 new_date
  call date_2fits(old_date, new_date)

If there are conversions which will be used by more than one application 
to encode and decode the new date format. These could be included in the 
RPFITS library. (ATLOD in AIPS uses the AIPS routine JULDAY to convert to
Julian day. JULDAY still used only 2 digit years in AIPS 15APR97.)

Henrietta
1998-03-24