When you display a photo in the Photos App, the time it was taken and the location where it was taken (if present) are shown above the photo.
On a Mac, the time shown is the local time for the place where the photo was taken. However, on an IOS device, the Photos app uses the local time at the device’s CURRENT location. For example, I live in the Pacific Time Zone but shot some pictures in Europe a few weeks ago. A picture shot at 10:30 am in Paris, when viewed on my iPhone or iPad, claims to have been shot at 1:30 am.
Note that I discovered this using photos from my iCloud Photo Library.
The bug has been reported via Apple Feedback.