antedate

To occur before an event or time; to exist further back in time.

I suppose you know all about the fearful myths antedating the coming of man to the earth—the Yog-Sothoth and Cthulhu cycles—which are hinted at in the Necronomicon.

We therefore turn to the question whether defendant's prior convictions for burglary and attempted burglary could be used as the basis for an enhancement under [California Penal Code] sections 667 and 1192.7. Both prior convictions antedate the effective date of section 667.

To assign a date to a document or action earlier than the actual date.

Tomorrow when you leav’st, what wilt thou say? / Wilt thou then antedate some new-made vow?

To find earlier citational evidence for a term.

Furthermore, while OED entries are generally regarded as a good indication of when terms were first used in English, for 5 of the 7 terms the present research has been able to antedate OED’s earliest attestations, usually by a decade or more.

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

anticipation