an·te·date 
(ăntĭ-dāt′)
(ăntĭ-dāt′)tr.v. an·te·dat·ed, an·te·dat·ing, an·te·dates
1. To be of an earlier date than; precede in time.
2.
a. To assign to a date earlier than that of the actual occurrence.
b. To date as of a time before that of actual execution: antedate a contract; antedate a check.
n.
A date given to an event or a document that is earlier than the actual date.