when = いつ (itsu) When is your birthday? "あなた の たんじょうび は いつ ですか?” Anata no tanjyobi ha itu desu ka Anata no = your tanjyobi ha = birthday itu = when desu = is you can use 'ka' when you ask questions. 'いつですか(itudesuka)' is very useful! For example コンサートは いつですか？　When will the concert be held? しけん（試験）は いつですか？ When is this test scheduled to be held？ something event + itudesuka →When will the something event be held?

Just a slightly irrelevant sprinkle on top... If you put Ka after a question word like itsu or dare or do ko etc... it can mean... Itsuka sometime Dareka someone Dokoka somewhere Nanika something These are all nouns with no question asking force.