Measurement requires a certain degree of accuracy. Everything that is measurable has a beginning which in turn means it has an end. If there were no beginning or end then it could not be measured and certainly not with any degree of accuracy.

In the Beginning...
Time is an artificial construct that exists where there are constants. Without the rotation of the Earth and its revolutionary course around the Sun, how could we measure time, know our ages, or discern historical reference. Without an ability to gauge dimensional measurements such as distance or the existence of fixed points such as stars, time as we know it could not exist. Time is order and not chaos.
The ways we measure time are based on other factors outside of time. The measure of our life is dependent on the time that has been set into place at some distant point in the past. That point can be called "the beginning". What was there before a beginning? Chaos. Or perhaps we can say the non-existence of thinking reasoning minds. But then that becomes much like the proverbial tree falling in the forest where nobody is present. Does that tree make a sound? Does place without a reasoning being have time?
Day one. Year zero. In the beginning... That is when time begins.
What do you think? Does time exist if there is no one to measure it? Does time serve any benefit to anything beyond the reasoning mind that is desirous to organize its world?