antedate

Short definition from Wiktionary

Verb

1. 1
   To occur before an event or time; to exist further back in time.
2. 2
   To assign a date to a document or action earlier than the actual date.
3. 3
   To find earlier citational evidence for a term.

Noun

1. 1
   Prior date; a date antecedent to another which is the actual date.
2. 2
   anticipation