Show time correction

I’ve finally (with @ScruffR’s help) achieved my years long goal of achieving a time sync on the Core. It has had the added benefit of correcting the ±5-7s inaccurate initial time set by the particle cloud on boot. Setting it at some point AFTER boot seems to result in a completely accurate time which is fantastic.

I was wondering, if just for the sake of sheer love of data, is it possible to report back how much the time had drifted when the time is corrected?

That’s surely possible.

You can have a tight loop spinning to catch a seconds change.
Then you capture and millis().
After that you trigger a Particle.syncTime().
When that has come back you catch the next seconds change and compare the difference between the current and previous with the difference between the new and old millis() readings.