The analysis in bug 1255458 [0] found some quality issues with profileDate: * 161 times it is missing * 641 times it is < 10957 (but >= 0) (i.e. a date before the year 2000) * 101 times it is > 17167 (i.e. a date with year 2017+) * Examples of those issues are printed at [54] in the notebook 0: https://gist.github.com/georgf/c9f4824e5d3bbf112db7

I don't have any experience with how much clock breakage we expect on Android expect. Could the wrong dates simply be broken clocks? Or a buggy implementation of us getting the profile age? The 161 missing profileDates surprise me as we haven't documented it as optional.

We expect lots of insane clocks on Android. Older studies suggest 3.5% of devices will be more than an hour wrong, with around 0.25% being more than a day ahead. http://opensignal.com/reports/timestamps/

(In reply to Georg Fritzsche [:gfritzsche] from comment #1) > The 161 missing profileDates surprise me as we haven't documented it as > optional. Not documenting this is my mistake – the current algo [1] attempts to read times.json and return the value from there. However, if times.json does not exist or the value could not be read, it returns -1 until bug 1246816 is implemented. Do we want to keep this bug open for the instances of clock skew? [1]: https://mxr.mozilla.org/mozilla-central/source/mobile/android/base/java/org/mozilla/gecko/telemetry/TelemetryUploadService.java#210

The clock skew seems to be below the expected level, i can run that down in a bit more detail once we get proper release data. We should note the behavior in the documentation though to avoid surprises.

Note that this will have minor conflicts with the doc changes in bug 1249288, but they should be trivial to resolve.

Comment on attachment 8735844 [details] [diff] [review] Document that the 'core' pings profileDate field can be missing Review of attachment 8735844 [details] [diff] [review]: ----------------------------------------------------------------- Looks good to me! Note that I already landed bug 1249288. Thanks for keeping the docs up-to-date.