Time Measuring

According to archaeological evidence, at least 5,000 years ago, and long before the [blank] of the Roman Empire, the Babylonians began to measure time, introducing calendars to co-ordinate communal activities, to plan the [blank] of goods, and in particular, to regulate planting and harvesting. They based their [blank] on three natural cycles: the solar day, marked by the successive periods of light and darkness as the earth rotates on its [blank] ; the lunar month, following the phases of the moon as it orbits the earth; and the solar year, defined by the changing seasons that accompany our planet's revolution around the sun.