retroact

/ˌrɛtroʊˈækt/
verb
  1. To take effect from a date in the past; to apply retroactively.
    • The new tax law will retroact to the beginning of the fiscal year.
    • If the policy changes, it cannot retroact and punish actions that were legal before.
    • The contract clause allows the agreement to retroact to the date of the initial handshake.
Antonyms
What does "retroact" mean? | whatsthatwordmean | whatsthatwordmean