Why 3.5% Of Android Clocks Are an Hour Off

At OpenSignal, each datapoint we collect has two timestamps: the time the reading was taken and the time the reading was inserted into our server. Because we make extensive use of SQLite cacheing on devices, these times can be far apart - sometimes up to the order of weeks. The app reading time, however, should always be before the server insert time, otherwise you have an apparent violation of causality. When we noticed this happening occasionally, we took a closer look and found widespread dif...