Variation is pervasive in language. Men don’t speak like women. Plumbers don’t speak like stockbrokers. And the people who make announcements over supermarket PA systems seem to fall back on a variety of English unknown to the rest of the population.

In English, when we say that something is in front of us, we often mean that it’s in the future, while something which is behind us is in the past. This seems so natural to us that we rarely think about it. But the ancient Greeks did it the other way round. For them, the future was behind and the past was in front.
The answer appears to lie in the way that people perceive time. English speakers perceive time as standing still while we travel forward through it but the Greeks perceive themselves as standing still while time overtakes them from behind. So the future was still behind the Greeks and not yet visible while the past was already in front of them and hence visible.