[paulsherwin]

Phone clocks can be very unreliable. I don't know about iPhones, but Android phones set their clocks using the mobile phone network rather than the internet, and they only do it when the phone boots. You can get quite a lot of clock drift if you never reboot.

There are apps which will get the time from an NTP server, but an unrooted Android phone doesn't allow apps to set the system time so you have to do it manually, which is usually more of a faff than just rebooting every few days.