Hello! My name is*****
I am sorry for the issue you are experiencing. This is a software issue with iOS. To solve the problem, you don't need to have the phone replaced since you can solve it by yourself - what you need to do is either reset the phone to factory defaults or re-install iOS using iTunes. Unfortunately, both of those methods will erase everything on iPhone (photos, music, contacts, etc), so you will need to create a backup first. You can do that in iTunes as well.
To reset an iPhone to factory defaults, follow these instructions:
1. Tap on Settings and then tap on General
2. Scroll to the bottom and tap on Reset
3. Tap on Erase All Content and Settings
4. Enter the passcode if it has been set or just confirm the reset by tapping on Erase iPhone
5. Wait for a few minutes while the phone is being reset. Once done, you will need to set it up again. If you created a backup with iTunes, you can connect the iPhone to a computer and restore the backup. The date and time should now work properly.
In case you require further assistance, let me know.