Over the last year, at random times (though almost always occurring overnight) my cellphone will show the wrong time. The clock will be off by 1 hour, either ahead or behind. Sometimes restarting the phone will fix it, sometimes it doesn't. I've had alarms that never go off or go off an hour late or an hour early due to this issue. The issue is especially obnoxious, because I take a sleeping medicine that requires a second dose 4 hours after the first dose, so I rely heavily on the timer function to wake me up. This morning I happened to wake up and after seeing the time on a nearby dvd player was confused as to why my timer alarm hadn't gone off. When I checked my phone, sure enough the clock was showing that it was 2am (rather than 3am) and the timer showed I still had an hour left. I manually went into the settings and corrected the time, and unchecked the "Automatic date and time" and "Automatic time zone" options, and that fixed the time and the timer rapidly sped up and went off seconds later.
I've found other posts about this online, and people seem to be experiencing this with all types of android devices. Some people said the unchecking the Automatic date and time and time zone settings worked, others said it didn't. Some posts said that it was a glitch caused by putting phones in silent mode, and that if you left the ringer on the clock wouldn't glitch....which makes no sense at all, and I need my phone on silent in order to sleep, vibrations and noise would wake me up. I'd understand if people had their phones in Do Not Disturb mode and were upset that they didn't hear an alarm, but that's the intention of that mode; alarms have always been able to penetrate silent mode. The only posts I found that were able to fix the problem had phones that were rooted and their solutions only worked for rooted phones. Mine is not rooted but I need to be able to rely on my clock (and the functions related to it like the alarms and timers).
I should also mention that this glitch always happens when my phone is stationary, so it's not like I'm traveling and took it out of airplane mode and the time took a while to update. If it is the phone loosing its connection to the network, why would it loose its connection in the middle of the night while sitting on a night stand?
