Hello SATZZM,
Thanks for choosing the Apple Support Communities. We understand you're not able to change your date and time on your iPhone. This may be due to having your date and time set to automatic. Check out the resource below on how to change that to manual.
Change the date and time on iPhone - Apple Support
"By default, the date and time, visible on the Lock Screen, are set automatically based on your location. If you want to change them—for example, when you’re traveling—you can adjust them.
- Go to Settings > General > Date & Time.
- Turn on any of the following:
- Set Automatically: iPhone gets the correct time over the network and updates it for the time zone you’re in. Some networks don’t support network time, so in some countries or regions, iPhone may not be able to automatically determine the local time.
- 24-Hour Time: (not available in all countries or regions) iPhone displays the hours from 0 to 23.
To change the default date and time, turn off Set Automatically, then change the date and time displayed."
We hope this helps.
Cheers!