A coworker walked into my office today and asked if I'd take a look at a drive to see if I thought the former owner had tried to tamper with the contents. After a little "pokin' 'round" I exported the event logs and opened up my event viewer to look at them when I noticed another log on my box. Not the ones I'd exported, but a new event log that comes with a default installation of Office 2007. So naturally, I discarded the investigation that I was supposed to be doing and began investigating what interested me. My proclivity for doing things like this is the reason that my desk is a shambles, but that's a tale for a different day, on to the new event log!
OSession.evt isn't incredibly interesting, but it might be useful in an examination. Below there are two of the entries that I carved out. . . You'll note that the application (Word) and the times are identified. That might be useful in a case where time was an issue.
I have not yet figured out what the active time entry is. It does not appear to be something that would be associated with actually working in the program; the first entry below was me opening Word, putting in some text and then saving and closing the document - active time 0 seconds. The second entry is from the first time I opened up Excel. I'm not sure what I did there, but it was probably something to do with carving out a file and then opening it with Excel. I have not found anything official that documents the log, so I would be interested in links to reliable documentation.
I did not include everything from the log, but it appears on first blush to have all the same features that the "big 3" event logs have, so you can find times. Times associated with log entries are the times that you exited the program, so an entry at 1345:00 hours that was 901 seconds long would have started at 1329:59 hours.
ID: 0, Application Name: Microsoft Office Word, Application Version: 12.0.4518.1014, Microsoft Office Version: 12.0.4518.1014. This session lasted 20 seconds with 0 seconds of active time. This session ended normally.
ID: 1, Application Name: Microsoft Office Excel, Application Version: 12.0.4518.1014, Microsoft Office Version: 12.0.4518.1014. This session lasted 172 seconds with 120 seconds of active time. This session ended normally.