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 commentablaze commented
In my case, it was the images captured by my phone camera, which sync to OneDrive. I walked into the same issue, and I synced all files using OneDrive app. Once, all files were on my hard drive, I wrote a C# .NET program of 20 lines, and ran it. My date issue was a thing of a past in under 10 minutes. Here is my blog post describing the story and resolution: https://wildclick.wordpress.com/2017/01/14/fix-modified-date-from-file-name/