by the timeadvadverb: Describes a verb, adjective, adverb, or clause--for example, "come quickly," "very rare," "happening now," "fall down."
(at some point before)
到…时候为止 dào shí hòu wéi zhǐ
You better have your chores done by the time I get home or you're in big trouble. The traffic was so bad that by the time I got to the office I was 20 minutes late.