Old Survey Photograph 1950s

How is it that everytime we looked at a photograph we can tell instinctively approximately what year it belonged it? Is it the way people dressed? Is there any other tell tale clues?

I have been to many places and in each of those places, I have not been able to blend in. Maybe my physique has something to do with it but even then people have been able to tell people apart. We are able to tell who the strangers are in our society and even in our building. They emit a different aura, I guess. Anyway, this photograph is indeed taken in the 1950s of a group of Survey Department people taking part in the float procession. The dresses are a complete giveaway to a different era and a different time.