到时候【dào shíhou】

到时候 means "when the time comes, then". It refers back to a future moment that has just been mentioned or that both speakers know about, and says what will happen at that point. It is spoken and neutral.

到时候再说 is a set phrase for putting a decision off.

It goes at the start of a clause or after the subject.

Only the future

到时候 always looks forward. For "at that time" in the past, use 那时候 or 当时.

• × 去年我在上海，到时候我很忙 → 去年我在上海，那时候我很忙

Not "on time"

到时候 is not about being punctual. "On time" is 准时 or 按时.

• × 请到时候来上课 → 请准时来上课