This book explains how for thousands of years, the effort to measure time and to create a workable calendar was one of the great struggles of humanity, a conundrum for astronomers, mathematicians, kings, priests, and anyone else who needed to calculate for the harvest, tax collection, or religious sacrifices. Human beings have always been and still are struggling to count the days and weeks and years, to calculate the movements of the sun, moon, and stars, and to capture them all in a grid of small squares that spread out like a net cast over time. How this net was woven in different cultures over the millennia, and why, is the subject of this book. Illustrated.