…的时候【de shíhou】

的时候 turns a clause into a time phrase meaning "when" or "while". The "when" part goes first and ends in 的时候; the main clause follows.

The 的时候 part comes first

English can put "when…" at the end of the sentence. The 的时候 phrase has to go before the main clause.

• × 我住在北京我小的时候 → 我小的时候住在北京

Two subjects

When the two clauses have different subjects, each keeps its own, usually with a comma between.

After a noun or a verb phrase

的时候 also goes after a noun or a short verb phrase for an occasion.

的时候 or 以后

的时候 means the two things overlap in time. For "after", use 以后.

Asking "when?"

的时候 can't ask a question. "When?" is 什么时候.

• × 的时候你来？ → 你什么时候来？