There are four types of time frames you can assign to an event.
<ul>
<li><b>Interval</b> - when an event has a definite start and end time, choose this option.</li>
<li><b>Starts At</b> - when an event has a definite start time but an unknown end time, choose this one.</li>
<li><b>Deadline</b> - when the end of an event is more important than when it starts, use this one.</li>
<li><b>All Day</b> - when an event is defined more by the day it is on than when it starts or ends (e.g. holidays)</li>
</ul>