by then
  到那時
  Then adv.
  1. At that time (referring to a time specified, either past or future).
     And the Canaanite was then in the land.   --Gen. xii. 6.
     Now I know in part; but then shall I know even as also I am known.   --1 Cor. xiii. 12.
  2. Soon afterward, or immediately; next; afterward.
     First be reconciled to thy brother, and then come and offer thy gift.   --Matt. v. 24.
  3. At another time; later; again.
     One while the master is not aware of what is done, and then in other cases it may fall out to be own act.   --L'Estrange.
  By then. (a) By that time. (b) By the time that. [Obs.]
     But that opinion, I trust, by then this following argument hath been well read, will be left for one of the mysteries of an indulgent Antichrist.   --Milton.
  Now and then. See under Now, adv.
  Till then, until that time; until the time mentioned. --Milton.
  Note: ☞ Then is often used elliptically, like an adjective, for then existing; as, the then administration.