A Brief History of Time Measurement

Throughout history, the Sun, Moon, planets, and stars have provided us with a means for measuring the passage of time and determining the seasons, months, and years.

Little is known about prehistoric timekeeping, but ancient artifacts indicate that people off all civilizations, were to some extent, preoccupied with measuring and recording the passage of time.

Twenty-thousand year-old architectural remnants discovered in Europe indicate scratched lines and gouged holes in sticks and bones, possibly used to count the days between moonphases.

Sumerians in the Tigris-Euphrates valley (present-day Iraq) used a calendar five thousand years ago that divided the year into 30 day months, the day into twelve 2-hour periods, and these periods into thirty 4-minute parts.

Evidence suggests that four-thousand year-old Stonehenge was used to determine seasonal or celestial events, such as lunar eclipses and solstices.

Egyptian timekeeping was initally based on the moon's cycles. Later, however, they realized that the star we call Sirius rose next to the sun every 365 days. Thus, some 5000 years ago, they devised a 365-day calendar.

More than four thousand years ago, the Babylonians (present-day Iraq) used a year of 12 alternating 29 day and 30 day lunar months, giving a 354 day year.

The Mayans of Central America, however, relied not only on the Sun and Moon, but also on the planet Venus, to establish two calendars - one of 260 days and another of 365 days.

Modern civilization has adopted the 365 day solar calendar. A leap year occurs every fourth year (except century years not evenly divisible by 400). Leap years add an extra day to February to correct for minor inaccuracies in the 365-day year.