Time is a tricky subject. Throughout history, people have used many different kinds of calendars to keep track of it. Yet despite the differences, all of these calendars make use of the sun, moon, stars— or some combinations of them— to measure time.
For most of human history, it was impossible to use anything other than the lights in the heavens to keep track of time. Humans did not have accurate clocks that could carefully keep track of each passing nanosecond.
Only in recent times has it become possible to ignore the lights in the heavens and still accurately keep track of time. Computers are more than capable of keeping track of time without the need for the sun, moon, or stars. Yet even though we have this capability, the likelihood of starting such a practice is slim.
The rising and setting of the sun is too important of a part of who we are. If we arbitrarily decided to make each day thirty hours long, computers could keep track of the time, but it just wouldn't make sense. It wouldn't be practical. Imagine if the sun set at a radically different time each "day". Each "year", the seasons would arrive in different months. Everything would be a mess.
The calendar we use today, the Gregorian calendar, is more accurate than calendars of the past. The deeper understanding that we have of astronomy allows us to have leap days on a regular schedule (we even add in leap seconds sometimes). In spite of these advancements, a year is still the same length. It still takes roughly the same amount of time to go through spring, summer, fall, and winter as it did thousands of years ago.
Although our modern world has divided up every hour, minute, and second of the day, the sun still rises and sets. Time still passes, and the best way that there is to measure it is by using the lights in the heavens.
It has always been that way in human history. The lights in the heavens have always been the way humans have measured time. Why is this the case? Because that's how God ordained it to be. Take a look at this passage from Genesis 1:
And God said, "Let there be lights in the expanse of the heavens to separate the day from the night. And let them be for signs and for seasons, and for days and years, and let them be lights in the expanse of the heavens to give light upon the earth." And it was so. And God made the two great lights—the greater light to rule the day and the lesser light to rule the night—and the stars. And God set them in the expanse of the heavens to give light on the earth, to rule over the day and over the night, and to separate the light from the darkness. And God saw that it was good. And there was evening and there was morning, the fourth day.Humans have always measured time using the lights in the heavens because God has designed the universe in such a way that it is the only way that makes sense. It is the only way that uniformity can be present in human society; for that reason alone, I think we can be sure that until the coming of Christ, humanity will continue to measure time in the same way they always have.