My photos changed its date

Most photos in my shared iCloud Library changed the dates too, but only the timezone assigned to the photos has changed. This has been my main reason to stop using the Shared iCloud Photos Library.

The dates can also change, when you share photos with yourself from two libraries, and there are duplicates with inconsistent dates. When you merge a bunch of duplicates automatically without checking the dates, Photos might pick the photos with the wrong date as the keeper.

But your time travel pictures are suspicious. Dates in the future might be created for two reasons:

1. Either your system time may have been set to a wrong calendar in the "System Settings > Language & Region > Calendar" in one of your accounts using the Shared Library - check if the Calendar is consistent and correct for all your accounts.
2. Or you may have accidentally selected more photos than you intended, when you fixed the date for a photo. The problem is, that "Adjust Date & Time is not batch changing all selected photos to the same date and time, but shifting the date and time of all selected photos by the same offset. Thus we can easily move some photos to the future, if we include a photo in the selection, that does not need the date to be corrected.

It will be difficult to fix the wrong dates by a script, if there is no systematic change that can be fixed automatically. It will probably be easier to restore your Photos Library from the last backup you made, when the dates have been correct. But you would need a full backup of your library from a version that did not use "Optimize Mac Storage" for iCloud Photos, because iCloud Photos needs to be empty, when you restore the library from the backup, or the wrong dates will persist.

I rarely let Photos merge the duplicates automatically. I like the Duplicates album as a place, where I can find potential duplicates, but I always compare the suggested duplicates myself - frequently they are duplicates I have created intentionally and want to keep, for example, differently cropped or edited versions of the same photo. And Photos cannot know, which of the metadata are correct, if the two duplicates are having different titles, different keywords, or different dates, or different locations. I prefer to check the duplicates myself for inconsistent metadata and fix them, before I merge the duplicates.

Where is the Photos library stored?

The_Muse wrote:

It’s in the default, my home pictures folder…..

That is the best place. Do you have a backup from the time the dates have been correct, so you can look them up?