[AccessD] How to Deal with Time Durations

In a new app that I am creating, of which you will probably hear ALL
about it over the next few weeks :), I have to keep track of event
durations.

Right now I have a field for the start time, and one for the duration.
Both are Date/Time fields.

The durations for the event can last from 1 second all the way up to
many hours, and possibly even days.

Should I actually be storing the start and end time and calculating the
duration? 

The duration can be entered as either the actual duration or the actual
end time.

If you have done something like this, how have you handled it?

Thanks,

Bryan Carbonnell
bryan_carbonnell at cbc.ca