WFC: Year-2000 issue

[Arnold Rots]

Since nothing much appears to be happening, let me try to force
the discussion by proposing that we support the proposal of the
European FITS committee with the following changes:

All references to UTC are to be deleted and replaced by the
following provisions:

1. Use of the keyword TIMESYS is strongly encouraged.  It will set the
   time system for all time related keywords and data in the HDU.
   Initially, Officially allowed values are: UTC, TAI, ET, TT, TDT,
   TCG, TDB, TCB.

2. The preferred value is "TT" which is considered equivalent to "TDT"
   and "ET", though "ET" should not be used for data taken after 1976.

3. If the TIMESYS keyword is absent or has an unrecognized value,
   a value of "UTC" will be assumed for dates starting in 1972.

4. The use of the "Z" qualifier in DATE-OBS is discouraged: if the
   keyword TIMESYS is missing, it is implied; if TIMESYS is present and
   has a value other than "UTC", this constitutes an inconsistency.


The only issue not addressed is that of the calendar.  What are the
arguments against mandating Gregorian calendar?  If its solves
ambiguities without placing undue restrictions, I would not object
to such a mandate.

  - Arnold Rots