Function: run-at-time

Perform an action at time TIME.
Repeat the action every REPEAT seconds, if REPEAT is non-nil.
TIME should be one of: a string giving an absolute time like
"11:23pm" (the acceptable formats are those recognized by
`diary-entry-time'; note that such times are interpreted as times
today, even if in the past); a string giving a relative time like
"2 hours 35 minutes" (the acceptable formats are those
recognized by `timer-duration'); nil meaning now; a number of
seconds from now; a value from `encode-time'; or t (with non-nil
REPEAT) meaning the next integral multiple of REPEAT. REPEAT may
be an integer or floating point number. The action is to call
FUNCTION with arguments ARGS.

This function returns a timer object which you can use in `cancel-timer'.