[Colin2B]

ok, just to be clear.
If you travel from home to nearby town and it takes 1hr then return journey is also 1hr. Total journey time (round trip) is 2hr, but the difference between the 2 journey times is 0, in other words they are the same.
Sorry to labour this but we've got to be clear to avoid misunderstandings

[jeffreyH]

If we take two vectors V1 and V2 this can be demonstrated. V1 starts at the origin [0, 0] and has an endpoint at [2, 2]. Vector V2 starts at [2, 2] and has its endpoint at the origin [0, 0]. To simplify the calculation we can translate V2 to The origin so that it starts at [0, 0] and its endpoint is at [-2, -2]. We can then simply add the vectors together using the endpoint values. [2, 2] and [-2, -2]. As can be seen the addition of 2 and -2 in both cases results ultimately in a null vector with both starting and ending points at [0, 0]. This indicates a velocity of zero for the round trip which could imply no time if you didn't have all the information about the past states of the system. Here information about the system is lost and so shows that information is generally not conserved with the flow of time.

[guest39538]

ok, just to be clear.
If you travel from home to nearby town and it takes 1hr then return journey is also 1hr. Total journey time (round trip) is 2hr, but the difference between the 2 journey times is 0, in other words they are the same.
Sorry to labour this but we've got to be clear to avoid misunderstandings

Yes exactly that.