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 ]

n. The assignment of a date to something at a time when it could not have existed or occurred.
Syn. -- anachronism, mistiming. [ WordNet 1.5 ]