A Russian Phrase for Asking About Someone's Birthday: "Когда у тебя день рождения?"

"Когда у тебя день рождения?" means "When is your birthday?" and it's the basic Russian expression used to ask someone when their birthday is. It's a handy conversation starter. To answer, you can say something like "Мой день рождения в мае." (My birthday is in May). To wish someone well, say "С днём рождения!" (Happy birthday!).