This paper is a comparative study based on the linguistic evidence in Vedic Sanskrit and Homeric Greek, aimed at reconstructing the space-time cognitive models used in the Proto-Indo-European language in a diachronic perspective. While it has been widely recognized that ancient Indo-European languages construed earlier events as in front of later ones, as predicted in the Time-Reference-Point mapping, it is less clear how in the same languages the passage took place from this ‘archaic’ Time-RP model or non-deictic sequence, in which (...) future events are behind or follow the past ones in a temporal sequence, to the more recent ‘post-archaic’ Ego-RP model that is found only from the classical period onwards, in which the future is located in front and the past in back of a deictic observer. Data from the Rigveda and the Homeric poems show that an Ego-RP mapping with an ego-perspective frame of reference could not have existed yet at an early Indo-European stage. In particular, spatial terms of front and behind turn out to be used with reference not only to temporal events, but also to east and west respectively, thus presupposing the existence of an absolute field-based FoR which the temporal sequence is metaphorically related to. Specifically, sequence is relative position on a path appears to be motivated by what has been called day orientation frame, in which the different positions of the sun during the day motivate the mapping of front onto ‘earlier’ and behind onto ‘later’, without involving ego’s ‘now’. These findings suggest that early Indo-European still had not made use of spatio-temporal deixis based on the tense-related ego-perspective FoR found in modern languages. (shrink)