Best way to capture state change times that are *not* now?

[David Masterson]

'C-u C-c C-t' forces a log note to be included with the state change,
but the state change log note is always *now* (CMIIAW).

Is there a way to change the state on a todo and have it ask for a
date/time to go with the state change?

Reason: I often don't get to change todo' state to DONE until long after
it was done.  I'd like to set the date/time to when it really happened.
-- 
David Masterson