Wanted to provide an update here.
First of all, if you are running into bugs (like all your photos have the same date) please reach out to support. If you’re on mobile, you can shake your device, if you’re on the web, you can use the settings cog.
As for the ability to change metadata on photos, that’s not something we currently have on the immediate roadmap.
An error occurred while saving the commentDSP commented
If using the onedrive app, then you can go into file explorer, and under the onedrive folder you can then select all the files in the relevant folder. Once the multiple files have been selected, right click and select properties, then select the details tab, scroll down to the header Origin and select into the 'date taken' option. You can now amend the year or date for all selected files.