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.Sandra Curry commented
Windows 10 - I have downloaded thousands of old photos and redated them. I have used by Picasa and Properties. either way at some point the dates change - all by themselves to dates that match nothing! It may redate the photo 2-1/2 years later ie. our wedding was redated from 5/2/1986 to 10/6/1988?? This isnt even the date they were downloaded. And batches of photos will not all change to the same date. This brings me to tears! Why is this happening???