Think about time. Seems pretty linear, doesn't it? Keeps moving inexorably from start to eternity, never turning back, always continuous linear motion.

Now, marvel at how easily and how often we slip into the habit of thinking of time not as linear, but as cyclical.

Picture an event that begins 24 hours in the future. You might ask, "When should I show up?"

The cyclical-minded person might reply, "Same time tomorrow."

But if you consistently think of time as linear, your reply would actually be, "Twenty-four hours from now", because the same time only happens once.

4 p.m. tomorrow is not the same time as 4 p.m. today. This date, last year is not "One year ago, today." It is one year ago.

Perhaps we tend to think of time as cyclical because all of our traditional means of measuring time move in a circular, cyclical manner. Daylight/nightfall, the Earth's rotation, analog clocks, seasons, the time it takes for the earth to orbit once around the sun, decades, centuries, millennia, and other nice round numbers.

Maybe this cyclical thinking is to our benefit: is there any way to measure, or even perceive, time without marking the passage of recurring phenomena? Would we have any semblance of modern civilization if these phenomena didn't occur in regular intervals?

Think of the innovations that humans have developed out of the need to accurately, or at least precisely, measure the passage of time.

Time, as we perceive it, is linear. Our measurements of time are necessarily cyclical.

decimetre says but the way we live, time does repeat itself due to our routines - in a sense it literally repeats itself seeing as time is basically a measure of movement

Anark says The answer to your question is here. We think of time as cyclical because we evolved in a periodic environment.