WatchDrift is an app that allows you to monitor your mechanical watches to see how much they gain or loose time... over time.
Whenever you adjust the time on your timepiece, you simply enter the current time as shown on your watch in the app, and it determines the difference in seconds between that time and the current computer time, and records it.
Now you have a history of your watch's time drift and can determine better when it its time to send it in for service.
The app shows graphs of your watch's time drift on the bottom of the window so you can tell how your watch is doing over time.