c. 40,000 – 2000 BCE
How did prehistoric people keep track of time?
Long before writing, people tracked time by the moon and the sun. Notched bones such as the Lebombo and Ishango bones may record counts of days or lunar months, and later monuments such as Newgrange and Stonehenge were aligned to the solstices so communities could mark the turning of the year.
Key facts
| Oldest possible tally | Lebombo bone, Eswatini, more than 40,000 years old, 29 notches |
|---|---|
| Possible lunar record | Ishango bone, DR Congo, about 20,000–25,000 years old |
| Oldest known lunar 'calendar' monument | Warren Field pits, Scotland, about 10,000 years old |
| Winter solstice alignment | Newgrange, Ireland, built about 3200 BCE |
| Solstice alignment | Stonehenge, England, main stages about 3000–2000 BCE |
| Lunar month | about 29.53 days |
| Solar year | about 365.24 days |
Time came before clocks. For most of human history, the only clocks were the sky: the daily swing of light and dark, the 29½-day cycle of the moon, and the slow drift of the seasons. Hunters, gatherers and early farmers who could read those cycles knew when game would move, when rivers would rise and when to plant.
Counting on bone
The oldest objects that might record time are notched bones. The Lebombo bone, a baboon fibula found in the Lebombo Mountains on the border of Eswatini and South Africa, carries 29 notches and is more than 40,000 years old. Twenty-nine is close to the number of days in a lunar month, which is why it's often called a possible lunar calendar. It may also simply be a tally, and archaeologists still debate what was being counted.
The Ishango bone from the Democratic Republic of the Congo, roughly 20,000 to 25,000 years old, has notches arranged in columns. Some researchers read them as a six-month lunar record; others see arithmetic, since one column holds the prime numbers 11, 13, 17 and 19. Engraved plaques from Ice Age Europe, such as the Blanchard bone from France, show spirals of marks that have also been read as moon phases.
What these objects show for certain is a mental leap: people had started to store information about time outside their own heads.
Moon to sun
Farming changed what mattered. Crops follow the seasons, and seasons follow the sun, not the moon. A lunar month drifts against the solar year by about 11 days a year, so a community that planted by moon counts alone would soon plant at the wrong time.
The earliest known attempt to reconcile the two is at Warren Field in Aberdeenshire, Scotland, where hunter-gatherers about 10,000 years ago dug a row of 12 pits that appear to track the phases of the moon, re-set each year against the midwinter sunrise.
Monuments that keep the year
Later farming societies built the solar year into stone. At Newgrange in Ireland, built around 3200 BCE, a small opening above the entrance lets the rising sun shine down the passage into the central chamber for a few minutes around the winter solstice. At Stonehenge, the main axis lines up with sunrise at the summer solstice and sunset at the winter solstice. Neither is a clock in the modern sense; they are calendars that mark the year's turning points, which were also times of gathering and ceremony.
Claims that much older sites, such as Göbekli Tepe in Turkey (about 11,000 years old), were built as observatories are interesting but far less certain.
From observation to calendar
As farming villages became cities, keeping the calendar became a job for specialists. Priests and officials decided when festivals, taxes and planting began. The calendars that followed in Mesopotamia, Egypt, China and Mesoamerica all had to solve the same problem those first pits and stones tackled: fitting whole months into a year that doesn't divide evenly.
Questions people ask
What is the oldest calendar in the world?
The oldest known site that seems to work as a calendar is Warren Field in Scotland, about 10,000 years old. Older notched bones, like the Lebombo bone, may record lunar counts, but that's an interpretation rather than proof.
How did cavemen tell time?
By the sky: day and night, the phases of the moon, and the position of sunrise along the horizon through the year. Some marked counts on bones or sticks.
Why didn't early farmers just use the moon?
Twelve lunar months add up to about 354 days, 11 days short of the solar year. A moon-only calendar slips through the seasons, which is a disaster for planting.
Sources
Last updated October 18, 2026. Found an error? Tell us.