Just installed version 10.5 and having the same problem.
Note: It is not that Shift + Alt + D does not work. It works, but it puts the date in US format, not the OS format as it used to, and there is no option that I can find to change that.
I also see that the date format in the reminders pane is also all screwed up.
I installed the Legacy version and the issue is fixed. If this does not get fixed in the official release, I will cancel my sub.
If there is somewhere else I need to post this to get the Dev's attention, please post it here so I can go there.