Time is real subjective. As with anything that is measured there must be a standard to base that measurement on. Time is no different, what is different is that the standard we base that measurement on is subjective. Do we base it on the cycles of the moon? Do we base it on seasonal changes? Do we base it on the Earth’s rotation around the Sun?
There are useful mechanics to measuring time, regardless of what the standard is that we use to measure it. Thousands of years ago it was important to know when to plant and harvest the crops. Today we measure it in much finer detail for just about every aspect of our lives. Time is a measure of human functionality. Before mankind needed to measure time, time still existed and passed just as it does today, but with far less fanfare. This was because it was less critical to day to day life.
When it started to get cold, the leaves on the trees would change signaling the change of seasons. This triggered the migratory survival instincts common in most species. Animals would roam from cold to warm, avians would migrate to their warmer climates and life would work must as it did today. Cycles of life that had no dependence on time and instead depended on the signs of the environment for day to day living.
Science has shown us the even our measure of time is subjective relative to the universe. Universally time is not the constant that we are familiar with in our daily lives. Speed and gravity can alter how fast or how slow time as we understand it moves. Large gravitational fields have the effect of slowing time, at least time as we know it. A similar effect occurs as objects accelerate close to the speed of light. These two circumstances alone make the concept of time subjective.
From what we have learned about time and how it relates to the universe is simply the tip of the iceberg. Space and time are proven to be directly tied to each other. Yet even with scientific proof of this knowledge we know so very little about how time and space truly relate to each other. Our understanding of time itself is so limited that we have to impose our own subjectivity to it so that we can comprehend its nature. Time is one of the most underused aspects of the universe strictly because of our lack of knowledge of it.
Is time subjective or real? In the end it’s all relative. It’s real when we need it to be real. In the end, it’s a subjective element of the universe that is real when it is convenient to our needs.