Short answers, pulled from the story.
Time is the continuous progression of existence that occurs in an apparently irreversible succession from the past, through the present, and into the future. Scholars have struggled for centuries to define time without circularity because it serves as a fundamental component for measuring other quantities like velocity.
Artifacts from the Paleolithic era suggest humans used the moon to reckon time at least 6,000 years ago. Early lunar calendars contained either twelve or thirteen months totaling 354 or 384 days respectively.
Einstein reinterpreted physical concepts associated with time and space in 1907 to challenge Newtonian ideas of absolute time. Special relativity postulated the constancy and finiteness of light speed for all observers regardless of their motion.
Many ancient cultures particularly in the East viewed time as a recurring pattern of ages or cycles where events repeated themselves predictably. Islamic and Judeo-Christian worldviews generally regard time as linear and directional beginning with God's act of creation.
This time directionality is known as the arrow of time and manifests through radiative entropic and weak forces. The second law of thermodynamics states entropy must increase over time within isolated systems evolving toward larger disorder rather than order spontaneously.