I am running two raspberries (installed from NOOB) as dataloggers in a proof of concept, and I rely on timing for timestamping data-entries, and of course for running cronjobs. The berries are running without any internet connection.
Now - recently I noticed one of them had set the system time 3 months back - and moreover I discovered that it resat the time on every boot.
By playing round a little, I found that if I did timedatectl set-ntp false - it would NOT reset the time, but rather keep ticking.
What is the recommended (surefire) way of ensuring correct system time ?