time zone object

[Olson, Arthur David]

	As John Cowan pointed out, HTTP would suffice as a low-level
protocol 
	for access to zone tables across the net, but we also need to
identify
	authoritative sources of up-to-date information; and specify
caching 
	of retrieved information with preference for the cached data up
to an 
	expiry date.  This requires representing the expiry date in the
cached
	file.  Does the "zic" format permit a datestamp?

There are bytes "reserved for future use" at the front of the file.

				--ado