Terminus ante quem

A terminus post quem is the earliest date the event may have happened or the item was in existence, and a terminus ante quem is the latest. An event may well have both a terminus post quem and a terminus ante quem, in which case the limits of the possible range of dates are known at both ends, but many events have just one or the other. Similarly, a terminus ad quem 'limit to which' is the latest possible date of a non-punctual event (period, era, etc.), whereas a terminus a quo 'limit from which' is the earliest. The concepts are similar to those of upper and lower bounds in mathematics.