Hmmm. Let us suggest that matter and energy (both of which were created at the big bang) exists not outside the Universe, but are contained within it. Now matter and energy are subject to time and space. Time is something we define as events/change etc. Eternity, however, must exist outside Time and space, because, by definition, it is something that does not change/alter, and, therefore cannot be part of the Universe. What do you think of this idea?