Here is a thought experiment that I was trying out today.
Question
Assume that we are in a society where there is no concept of time. You have to meet a friend. How do you two sync up so that you can meet each other. Remember that you do not have a concept of time, hence you cannot tell him 'meet me below the fourth coconut tree at 3 PM today'.
Answer (one of the many)
One answer that I think might be feasible is that you tell your friend that you will let off a firecracker (or some signaling device) when you leave your home and you will let off a firecracker after every 500 meters.
Applications of this problem
How do ants sync up between themselves ? i.e. how do they decide 'this is the time the house owner makes tea and spills some milk on the counter'