Printing time in "at" format?

[Roy Smith]

I need to talk to an API which requires (for reasons totally beyond my
comprehension), time specified in "at" format, i.e. the format
accepted by the unix "at" command.  This allows you to do such bizarre
things as use "teatime" to indicate 4:00 PM.  The best I can find for
a specification is http://tinyurl.com/d5vddoa.

Before I dive into this too far, has anybody already written some code
which formats times like that?