I'm speaking of the most well-known Dragon Break, the one that lasted between 1E 1200 - 2208. http://www.uesp.net/wiki/Lore:Dragon_Break It was a convergence of multiple realities, all occurring seemingly at once, interacting with each other until the present reality was formed. Imagine a trail of sugar, all the grains laid out in a line. This is linear time. But when you put the sugar into tea and stir, past, present, and future have no meaning. This is eternity. We cannot say for certain what happened before the Dragon Break, because history has been rewritten. The events of the past that occurred in one dimension may not have happened in others, or in what we consider to be our original timeline, but after the Dragon Break, it might've happened without our knowing. It could also account for various anomalies in time, like Pelinal's armor, which was said to be from the future. What else can you think of that the Dragon Break might explain?

Dragon War, for starters. No one seems to be able to accurately pinpoint when it occurred. If we're working with the assumption that some events got dropped from history because of the Dragon Break, then I suspect that the Dragon War happened on a timeline that didn't make the "final cut," if you will. However, some of its effects carried over, such as Alduin being trapped in a time-wound, Paarthurnax, and the 3 champions making their way to Sovngarde.

That, and using time to ensnare the first of the firstborn of the Time Dragon doesn't sound like a good idea, no matter how successful it is.

Akatosh.

The Break was caused by the Selectives 'dancing on the Tower' in an attempt to remove merish influences from Auri-El.
They succeeded, in a fashion.