A value of Tense Property assigned to the designated element in the clause when the meaning selected for the clause is that intended to locate the event spoken about as anterior to the deictic centre of the utterance. Most commonly, this tense meaning is referred to as 'past', because in absolute tense systems the deictic centre is the moment of speech. However, in relative tense systems, where the deictic centre can be moved to any point on the time line, it is more appropriate to refer to this temporal relation as 'anterior'.
The anterior temporal relation may obtain either in 'simple' or 'perfect' contexts. Modelling of this distinction originates from [Reichenbach 1947], who suggested using a third point in time, 'reference point', to capture all possible tense distinctions. In all 'simple' temporal relations, the reference point coincides with the location of the event spoken about. 'Perfect' tense meanings are created when the reference point is separated and moved away from the event time, thus altering the viewing of the temporal location of the event even though the event's actual location with respect to the deictic centre remains the same.
A common instance of an anterior temporal relationship obtaining in a 'perfect' context occurs when the reference point is moved away from the event time and located instead at the moment of speech. The event time is still anterior to the moment of speech, but it is viewed against a stretch of time which began at the event and continues up to the moment of speech --- e.g. the English I have read this book, I have seen John --- hence the interpretation that the event has an effect or is in some way still relevant at the moment of speech. In some languages (e.g. English) this tense meaning is labelled as (one of the uses of the) Present Perfect, in others (e.g. Polish) this meaning may be collapsed with the 'simple' anterior meaning and labelled simply as Past.
Typically, for a tense value to be labelled as Past Tense, the tense meaning has to minimally express the anterior temporal relationship, although it may additionally express other temporal relationships or aspectual and/or modal meanings. For example, when the usage of the Past Tense value is restricted to a semantically defined domain, it is conventional to add a further qualification to the label of the Past Tense value (e.g. Past Imperfective --- when the anterior temporal relationship is necessarily combined with an aspectual meaning of the Imperfective Aspect value, and grammaticalised as a single TAM category in the language).