OS X El Capitan Update Release Times
There is no official OS X El Capitan release time for small updates, but it is predictable. Even though Apple does not typically announce a specific download time small or large updates they come at the same general time unless there is an event.
The company normally starts to offer a major software update at 10 AM Pacific or 1 PM Eastern. If you are looking for the latest update, you can check after these times. If you are upgrading to OS X El Capitan in 2016, the timing doesn't matter as much.