When viewing an event which has Time shift enabled, the viewer may pause playback or seek backwards up to 4 hours while the event is live. In case the event is longer than 4 hours, the period of the event before the last 4 hours won't be available to the Time shift function.
How to Enable
To enable Time shift for a new event check the Time shift checkbox in the New Live Event wizard.
Time shift can't be enabled or disabled for existing (already scheduled) events but you can see whether it is enabled or not on the Information tab of your event.
You can choose whether you want Time shift to be enabled or disabled by default for new events under Live on the Settings page.