The study of heavenly cycles is common to most ancient cultures. The ancient Egyptians, Chinese, and Babylonians all tried to make sense of the year. But it fell to the later Mesoamerican Maya to create a series of calendars that could be cross referenced. In doing so, the Maya discovered many strange numerical harmonics. Their lunar calendar was extremely accurate - far more so than the Greek Metonic cycle; they tracked Venus to an accuracy of less than a day in five hundred years and their tables could have been used to predict eclipses seven hundred years in the future. This book will provide a much needed compact guide to the Mayan calendar systems as well as covering the essentials of calendar development throughout the world.