I needed to find out the number of hours I had worked on for a project. As I worked, all my activity was recorded with a message in the commit with the git repository. To gauge the amount work, I needed to see roughly the number of changes made in lines of code as an underestimate of time spent (lets not exclude pen and paper stuff!). Using a viewer application such as gitx made the process much easier, even though it is not designed for auditing hours. One does appreciate a nicely laid out interface. 

I could not find anything that quantitatively estimates number of hours based on a git log. It would be interesting to measure how much work a commit actually constitutes. There is even more information available about the work done using the timestamps on each file.