If you install ubuntu with window (dual boot)
the window's time is changed.
It is because
Window interpret the time based on RTC(real-time clock),
but ubuntu interpret it based on UTC(Universal time coordinated)
below command is using RTC on ubuntu.
Set below so that it can be saved even after reboot
sudo vi /etc/default/rcS
In /etc/default/rcS, type first line like this
sudo vi /boot/grub/grub.cfg
In /boot/grub/grub.cfg, find Windows 10(loader)
after chainloader +1 in windows 10 function, write
save and reboot.
In my case, when using reboot in ubuntu, grub is infinite
so I don't using reboot. Instead, using power off and passively power on my computer