This would also be really helpful for me.
This (somewhat) works for queries in english.
https://kagi.com/search?q=mothers+day+2024 returns "Sunday, March 10, 2024", which is true in the UK, but probably not in most of the rest of the world.
https://kagi.com/search?q=muttertag+2024 (German) does not return any quick answer / instant answer.
It would be nice if this feature worked for different languages, as well as returning the answer that is correct in the currently selected region.