Can't think of anything rather than this:

Пять лет тому назад. Тому might refer to some event that itself could happen at any time stamp. So this phrase can be heavily used in a story telling to tell about an event that happened within the story's time frame.
Пять лет назад. Well it's just five years ago.

All in all these two are pretty much interchangable, both can mean the same thing.