It synchronizes with an atomic clock, measures and records the difference, and displays graphs of all the data points you've recorded. - Uses best-fit analysis to accurately calculate how many seconds your watch gains or loses per day - Displays graphs of rates and variance - Can track multiple watches simultaneously - Saves data in CSV files that can be opened with any spreadsheet software Watch Tracker is made by the developer of tChess (the chess app that was featured in Apple's "Learn" commercial for the iPad) and Learn Chess (the Apple Staff Favorite e-book).