As if we were somehow separate from everything around us. We're a part of the universe, moving along as the rest of it does. Our memories are a function of our brains, and our brains are wholly subject to natural laws. Since natural laws establish entropy, we likewise experience that entropy and are a component of it, same as everything else around us. Consequently, we 'remember' the past since we existed in it as such, but what we consider the future has not occurred yet from our perspective. The future is our future, and we have no way of overcoming this. Has the future happened? Is there any point of view possible from which the future has already occurred? I think it would have to be outside of the universe as we know it for that to be, but there is no telling what might be beyond the universe, if anything, and you have to wonder whether it would be possiblet observe anything within the universe from outside of it anyway. If the universe is a singularity, then I expect there is no way. Singularities are wholly destructive and unapproachable, and at the same time practically invisible and unobservable.
A measurement of time is simply a measurement of movement, or more precicesly, a measurement of change if you want to get technical. Nothing more, nothing less.
The more I think about how we calculate time the more silly it is...we ignore billions of years of time on Earth and decide to start 2014 years ago as if that moment in time has any scientific meaning. I'm back to my statement that local time systems are exactly like local languages in which the 'other' language is meaningless unless the person can relate or make conversion, which for a space traveler is impossible since they won't know the local time systems until they arrive. We are guided by the light and dark of each Earth day instead of a Universal time used by everyone...
