Is it normal to say: "What do Jews do on this day?"?
I think it should be, if it's some holiday or whatever and they do the same things on this day every year
Yeah, I have thought exactly the same :)
Yes, like Vinnfred said, it's normal if you're talking about a special day of the year -- a holiday or a day with traditional activities.
Це основний переклад. Інший варіант - What are Jews doing on this day?
У суботу? Нічого
We never call Jews іудеї. They are юдеї.