Many iPhone users after upgrading to iOS 11 are facing issue that iPhone is showing wrong timezone. The issue is while iPhone Time Zone set to "Set Automatically" to OFF , iPhone will revert to home country time after a restart or switching back from AirplanMode. The time zone reverts in iPhone is faced only after upgrading to iOS11. This sometimes causes to miss an alarm, reminder or important meeting.
The issue is even affects latest iPhone 8 + and iPhone X. iPhone X on iOS 11.2.5 seems to switch ‘auto time zone’ setting back on a few hours after a restart. The issue is very annoying as once you restart your phone it will reset itself to whatever time it wants. The issue is more prominent if you have bought a phone from one country and using it in some other country.
Many users tried set the date time "set automatically" to be off (settings>privacy>location services>system services) but even this does not seems to fix the issue as after sometimes it will change back to “set automatically”. iPhone mysteriously randomly changes settings back to auto. Surely Apple need to fix this as the current time is basic functionality and many users are facing many problems as they have lost the ability to control this basic functionality on their iPhones.
How to fix iPhone automatically changes timezone:
Fix 1: Remove app permission to use location services
For many users turning off location services helped to fix the issue eg like Facebook etc. Make sure you go to Settings > Privacy > Location Services > System Services > Setting Time Zone and toggle this.
Fix 2: For calendar related issue
In iCal there is ‘time zone override’ option, of you chose to select that iPhone calendar will stand in one location. But this would not fix issues related to alarm, email timestamp etc.
There are no permanent fix for the issue and Apple seems to looking at this issue so it is recommended to keep upgrading to latest iOS releases.