Unexpected change of system time

[alf@emcom.no]

One Revpi Connect is logging sensordata on a ship.
It is in a remote part of the ship and not connected to a network.
It has a WiFi USB and acts as an ap for servicepeople to connect and download the logs.
All of a sudden, sometime during the summer (probably around end of July) the system time was set back to some time in April.

So two questions :
a) what could possibly be the reason ?

b) what is the recommended way to permanently change system time ?
We have been doing :
sudo timedatectl set-ntp false
sudo timedatectl set-time '2019-07-09 13:01:00'

Any tips appreciated...
Alf

[dirk]

Dear Alf, this seams strange. The RevPi Connect has a built in RTC which is 24 hours buffered. So maybe you just have to synchronize it after a reboot? Maybe the ideas of this posts can help you.

[zhan]

Hi Alf,

before "All of a sudden", what have you done with the device ? Has it ever been powered off more one day ?
It seems this normally happens when linux can not read a correct date/time from RTC hardware which can be powered by a super capacitor only about one day.

One Revpi Connect is logging sensordata on a ship.
It is in a remote part of the ship and not connected to a network.
It has a WiFi USB and acts as an ap for servicepeople to connect and download the logs.
All of a sudden, sometime during the summer (probably around end of July) the system time was set back to some time in April.

So two questions :
a) what could possibly be the reason ?

b) what is the recommended way to permanently change system time ?
We have been doing :
sudo timedatectl set-ntp false
sudo timedatectl set-time '2019-07-09 13:01:00'

Any tips appreciated...
Alf