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Computers use a hardware component called RTC (Real-Time Clock), which is powered by an external battery, to continue counting the system time during power outages or when the system is turned off and on.
The T3-GEM-O1 board includes an RTC. If you do not use the RTC module, the system time will reset and start from 01/01/1970 when you cut and restore power to the board. If the board is connected to the internet, the correct time will be set after a while. If you want the time to remain accurate even without internet, you must use the RTC.

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Steps to Run the RTC

1

Connect the Battery

2

Send the Current Date and Time Information

Next, open a terminal via serial port or SSH. You must send your system time to the RTC module once using the following command.
gemstone@t3-gem-o1:~$ sudo hwclock -w -u /dev/rtc0
If the operation is successful, when you run the hwclock -r command, you should see an output similar to the following.
gemstone@t3-gem-o1:~$ sudo hwclock -r
3

Test

Turn off your board using the power button on the board or the poweroff command, and unplug the power cable. After waiting about 10 seconds, power the board back on and run the date command. If the displayed date and time are correct, the RTC is working properly.