verb (used with object), back·dat·ed, back·dat·ing.
to date earlier than the actual date; predate; antedate: Backdate the letter so he'll think I wrote it last week.
Origin of backdate
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
(tr) to make effective from an earlier datethe pay rise was backdated to August
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