That will depend on the album, where you are viewing the photo.
For example, Recents or Imports are sorting the photos by the date the photo has been added to the library, not the date the photo has been taken.
The Media Type albums and All Photos are sorting the photos based on the date they have been taken. Here the order should change, when you adjust the date, but it may take a while, until Photos will change the sorting. It may help to close and open Photos again to make it notice the changed date and time.
And you can sort any album you create yourself by the date the photo has been taken. There you should be seeing the changed date immediately, when you sort the album again.
But how have you been changing the Date and Time?
Have you changed the timezone or the time, or both? When you only change the timezone, the actual capture date will not be changed, as Photos is just converting the date to the other timezone. The date will just be displayed converted for a different time zone, but still refer to the same moment in time. if you want to shift the time to a different moment and in a different timezone, for example if the clock in the camera has been set incorrectly, you have to adjust both the timezone and the date and time.
You have used "Adjust Date & Time" as described here? Edit photos and videos on iPhone – Apple Support (UK)