I’ve found a few old forum posts about making the dublin core date field in such a way that items are able to be sorted by date (not the date added, but the date of the object). None of the answers I read seemed to be very straightforward… wondering if there’s a good solution out there.
For standardizing date entry, you might try the Element Types plugin. That should handle one side of your question.
The other side, sorting, will be a little different based on the precise needs you have. Changing up the url to the browse page is one straightforward approach that’s in the forums. Allowing the user to click a link that resorts the items is another that’s in there. So, what exactly do you have in mind?