24:00 versus 23:59:59--insights?

[Olson, Arthur David (NIH/NCI) [E]]

There are a few places with rules such as "... lastFri 0:00 ..." that
should be "... lastThu 24:00 ..."
One possibility is to rewrite the rules that way; doing so buys error
messages from pre-1998 versions of zic.
Another possibility is to rewrite the rules as "... lastThu 23:59:59
..." which works with pre-1998 versions of zic but is a second off. A
third way is to use 24:00 and, where it is used, include a comment about
either upgrading zic or using the 23:59:59 dodge. I'd appreciate any
insights on how to go forward.
 
				--ado