terminus ante quem
ˌantɪ ˈkwɛm/

Terminus post quem (“limit after which”, often abbreviated to TPQ) and terminus ante quem (“limit before which”, abbreviated to TAQ) specify the known limits of dating for events. A terminus post quem is the earliest time the event may have happened, and a terminus ante quem is the latest.
noun
noun: terminus ante quem

the latest possible date for something.
“1467 represents a terminus ante quem for the death of Fahreddin Acemi”