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.Lori Bierman commented
This problem is incredibly frustrating. Every year I make a calendar for my significant other with photos of us and things we did in that month. Not being able to trust the dates in OneDrive makes this task needlessly complicated.