My Casio Oceanus T4000 is regulated to run with about 1 second a month error(*).

Which the watch delivered for the past year.

Suddenly, overnight the watch became 1 second slow (30-times greater error than normal).

My first thought — OMG, regulation drifted!

But upon inspection, it turned out the watch inadvertently Bluetooth-synced with the phone. One accidental SYC button press!!..

Lesson about Casio Watches: who knew it could be that inaccurate at times.

Lesson for me: kill Casio…

From real life: Trimmer Capacitor vs Bluetooth Atomic