To manually specify a time zone, you’ll first disable the automatic date and time option on your iPhone.

• To do so, first, launch the Settings app on your phone. In Settings, tap “General.”

• On the “General” screen, tap “Date & Time.”

• When the “Date & Time” page opens, turn off the “Set Automatically” option.
• If you find that “Set Automatically” is grayed out, check out the final section in this guide to learn what to do.

• Now that the automatic option is disabled, specify a new time zone by tapping the “Time Zone” option.

• On the “Time Zone” page, in the text box at the top, type your city’s name. Your iPhone will use the date and time for that city.
• Once your city appears in the list, tap it.

You’ll be back to the “Date & Time” screen, and your iPhone now uses the time and date for your selected city (time zone).

And that’s all there is to manually changing the time zone on an iPhone.