The Collaborative International Dictionary of English v.0.48:

Misdate \Mis*date"\, v. t. [imp. & p. p. Misdated; p. pr. &
   vb. n. Misdating.]
   1. To put a false or erroneous date on (a document). --Young.
      [1913 Webster]

   2. To assign an incorrect date to; as, the fall of Troy was
      misdated by medieval writers.
      [PJC]