Is there a (semi-)standard Unix command that would sleep until the time specified on its command line? In other words, I am looking for something similar to sleep that would take wakeup time rather than duration.

For example: sleeptill 05:00:00

I can code something up but would rather not re-invent the wheel if there's already something out there.

Bonus question: it would be great if it could take the timezone (as in sleeptill 05:00:00 America/New_York).

edit Due to the nature of what I am doing, I am looking for a "sleep until T" rather than "run command at T" solution.

edit For the avoidance of doubt, if I run the command at 18:00 and tell it to wake up at 17:00, I expect it to sleep for 23 hours (or, in some corner cases having to do with daylight savings time, for 22 or 24 hours.)