I frequently arrange teleconferences with participants from several
time zones. In an effort to reduce confusion about the time of the
meeting, I try to publish the time in several relevant time zones.

But correctly calculating EST, PST, GMT, CET, and JST, for example,
requires too much thought. That's what computers are for. And since
I'm usually sending email reminders of the meeting time, that's
what Emacs is for.  And that's what this code is for.