Assumed: LG G5 phone, Android 8.0/Oreo (latest supported release), 2 batteries[br]
[br]
1 Shut down phone[br]
2 Swap battery[br]
3 Reboot[br]
4 Observe: time is wrong[br]
5 Log in[br]
6 Status bar upper right > Settings[br]
7 Scroll to bottom[br]
8 Tap System (2nd-to-last item)[br]
9 Select Date & Time (3rd item)[br]
10 If "Set automatically" on, uncheck[br]
11 Check "Set automatically" - time now correct