The Collaborative International Dictionary of English v.0.48:

Antedate \An"te*date`\ ([a^]n`t[-e]*d[=a]t`), v. t. [imp. & p.
   p. Antedated; p. pr. & vb. n. Antedating.]
   1. To date before the true time; to assign to an earlier
      date;; thus, to antedate a deed or a bond is to give it a
      date anterior to the true time of its execution.
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   2. To precede in time.
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   3. To anticipate; to make before the true time.
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            And antedate the bliss above.         --Pope.
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            Who rather rose the day to antedate.  --Wordsworth.
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