DATE-OBS etc.

[Jonathan McDowell]

I am inclined to think we should go with the ISO date format,
but I don't remember it and have a vague memory it had  some
not so nice features. Failing that, we should use the traditional
astronomical most-significant order of  yyyy-mm-dd; but since it
is to be human readable I think separator characters like - or / 
are a good idea.

I don't think DATE-ISO works because we actually need to replace
DATE-END  and DATE as well; let's replace the four letters DATE
with something else, since that will give us a general solution.
How about CALEN-OBS (or better yet CALEN_OBS since there has been
discussion in the high energy community about it being a good idea
to avoid - signs) for 'Calendar' which I think captures the
idea that it's a human readable thing. 

I don't think the IAU MJD thing should worry us, as I understand
it, it's not being forbidden, just not required in certain circumstances.
Nevertheless, I personally think that in the long term
we should use JD and not MJD, after all JD has several centuries
of being a standard while MJD is still basically an informal convenience.
But I suspect I'm in a minority on that issue.

   - Jonathan McDowell