Event duration, what is more effective start datetime end datetime, or 1 hr long?

[imagined]

I'm about to add Event Duration to the Calendar class.

There is two ways I believe I can approach this

Add MySQL column for EventEndTime. Example: StartTime 2009-11-20 08:00:00, EndTime 2009-11-20 09:30:00
Add MySQL column for EventDuration. Example: EventTime 2009-11-20 08:00:00, EventDuration 01:30:00


Which one if your opinion is more effective?

[actionAction]

Numero Uno, it seems more inline with your current setup. Date math sucks, easier just to show start and end times as you have been doing throughout.