The server is synced to a world clock and may play the file may at a slightly different time than your computer’s clock.
You should also remember that this file is being played over an actual live stream, so there will be the usual delays involved. Our server will fire off the stream at the appointed time, and the file will be playing, but it may take 30 seconds to get to the player where your viewer can see it. Also, when the file is finished playing, the stream will sever its connection immediately, and could cause the file to not finish showing in the player.
To prepare for this slight offset, we recommend that you add a few minutes of pre and post event content to the beginning and end of the file, and schedule the playback for one minute prior to the actual event start time. You could add a countdown (which sets expectations, and viewers love), or slides and music. These things also add a bit of transition to your event, which helps your stream look very polished.