The Collaborative International Dictionary of English v.0.48:

Then \Then\ ([th][e^]n), adv. [Originally the same word as than.
   See Than.]
   1. At that time (referring to a time specified, either past
      or future).
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            And the Canaanite was then in the land. --Gen. xii.
                                                  6.
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            Now I know in part; but then shall I know even as
            also I am known.                      --1 Cor. xiii.
                                                  12.
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   2. Soon afterward, or immediately; next; afterward.
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            First be reconciled to thy brother, and then come
            and offer thy gift.                   --Matt. v. 24.
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   3. At another time; later; again.
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            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.
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   By then.
      (a) By that time.
      (b) By the time that. [Obs.]
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                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.
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   Now and then. See under Now, adv.

   Till then, until that time; until the time mentioned.
      --Milton.
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   Note: Then is often used elliptically, like an adjective, for
         then existing; as, the then administration.
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The Collaborative International Dictionary of English v.0.48:

Till \Till\, prep. [OE. til, Icel. til; akin to Dan. til, Sw.
   till, OFries. til, also to AS. til good, excellent, G. ziel
   end, limit, object, OHG. zil, Goth. tils, gatils, fit,
   convenient, and E. till to cultivate. See Till, v. t.]
   To; unto; up to; as far as; until; -- now used only in
   respect to time, but formerly, also, of place, degree, etc.,
   and still so used in Scotland and in parts of England and
   Ireland; as, I worked till four o'clock; I will wait till
   next week.
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         He . . . came till an house.             --Chaucer.
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         Women, up till this
         Cramped under worse than South-sea-isle taboo.
                                                  --Tennyson.
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         Similar sentiments will recur to every one familiar
         with his writings -- all through them till the very
         end.                                     --Prof.
                                                  Wilson.
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   Till now, to the present time.

   Till then, to that time.
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