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

programming
1

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

There is two ways I believe I can approach this
[LIST=1]
[]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
[/LIST]

Which one if your opinion is more effective?