Select your library then FILE>OPEN LIBRARY>FROM BACKUP and you’re see a pull down list with all the autosaves available. As Bill said it only saves if something has changed so it’s accurate to about 15 min.
Why do you need to have such specific billing? Wouldn’t you at least bill by the hour or half hour minimum?
Me, I just keep it all in iCal. I’ve found some apps in the past that will produce an invoice from iCal data and write to iCal the timing data. But I’ve found tracking apps to be just as much trouble as entering the time myself. Plus, how do I discern a 30min search on iStock for just the right image and taking a break to web surf? Or getting emails with images from the client and checking my email on a lunch break?
And it’s all just more stuff to reinstall whenever I do a clean install every 6 mo or so.