A time of day along with a time zone.
Expresses things like "Seinfeld moved to 6:30pm EST.", while a plain Ofday
expresses something more like "I eat lunch at noon (in whichever timezone I'm in at
the time).".
Sexps look like "(12:01 nyc)"
Two t
's may or may not correspond to the same times depending on which date
they're evaluated.