[fitsbits] Start of the WCS Paper III Public Comment Period

[William Thompson]

One of the keywords introduced in this paper is MJD-AVG, representing the
average time of the observation.  If MJD-AVG is absent, then DATE-OBS is used in
its place, but the latter refers to the start of the observation.  Why not also
introduce a keyword DATE-AVG, with the same ISO 8601 format as DATE-OBS?

I say this mainly because I'm concerned that there is developing a split between
two different time-handling methodologies, one based on ISO 8601, and a
different methodology used within WCS, based on MJD.

William Thompson