date functions

[00771g-Lukas]

I am looking for a set of routines that will perform date manipulations.
Each date would have two representations; an external, which is just
your normal 01/01/89, or some such; and an internal, which would be
the number of days since some arbitrary day one. I would like routines
that would:

1)	convert from external to internal format. It would be nice
	(but not necessary) if various external formats could be
	used: 01/01/89, 01/01/1989, Jan 01, 1989, 890101, etc.
2)	Convert from internal to external format. It would be nice,
	etc.
3)	Return the month, day, and/or year from an internal format
	date.
4)	Return the number of days in a given month (handling leap
	years, etc.).
5)	Return the ordinal day of the year.
6)	Return the ordinal day of the week.

Is there anything like this available? TIA
-- 

	John Lukas
	att!ihlpf!lukas
	312-510-6290