Not until, only then: time + mới

You know mới as "just": Chị Lan mới tới. With a time word in front, it means "not until, only then": Mười giờ chị Lan mới tới. Lan didn't come until ten. It says something happened later than expected, or later than you'd like.

The time comes first, then the person, then mới right before the verb: Chín giờ tối em mới về. I won't be home until nine tonight. It works for the past and the future alike; the context tells you which.

Instead of a clock time, the first part can be a length of time or an event: Chờ nửa tiếng xe buýt mới tới. We waited half an hour before the bus came. Ăn xong rồi mình mới đi. We'll go once we've eaten.

Compare Mười giờ chị Lan tới, which just gives the time, with Mười giờ chị Lan mới tới, which adds "so late". For the opposite feeling, "already, as early as", use đã … rồi: Sáu giờ anh Nam đã dậy rồi. Nam was already up at six.