Sorry. Not sure what happened to my text at the end there. It should read "but there are some extensions that claim to do so. The link is good. Now, I haven’t used twig extensions before, so I’m not certain how to incorporate them into Grav. That’s something I need to look into.
Good news. According to the Grav source code, it looks like a sort_by_keyfilter is available. Give it a shot and let us know if it worked.
In your case, though, it won’t work as you expect because of your date formats. You’ll have to convert them to ISO or epoch format for the filter to work properly.