jackrae:
In the good (or was it bad) old days of mains powered clocks they were ideal for logging outages (of minutes or hours durations). All you had to do was ensure the clock was set to the correct time then view it several hours/days later. If there had been an outage, the clock was slow by the total length of outage duration. OK it wasn't rocket science but it worked.
I always used to have an inexpensive electric (synchronous motor-driven) clock on my workbench for just that purpose. Unfortunately, the ones I've had must have been cheap as well as inexpensive, after a couple years they'd get noisy and eventually stop or not keep accurate time. I have a relatively complex microcontroller-based system in place now that will notify me via SMS of power outages as they occur, but I might also go ahead and rig up one of these RTCs into a nice little self-contained device.