Broker Leveltime 

A databroker addon that simply stores and displays your played time for each level while you are levelling your character.

As of v1.0 it displays the point in time you reached a level and how long time you played a level.
It displays the last 5 levels in the tooltip.

In it's database I store the times for all levels so it can display them at a later time.

It will of course needs to be running at the time you level to be able to store the information. There is no way I know of to get this information after the fact.