Why are there 12 months in a year?
There are 12 months in a year because there are roughly 12 lunar cycles, from new moon to new moon, in one solar year. Early calendars were based on the Moon.
A lunar cycle lasts about 29.5 days, and 12 of them add up to about 354 days, close to the solar year of about 365 days. Many ancient peoples, including the Babylonians and Egyptians, used 12 months. The word month itself comes from the same root as moon.
The early Roman calendar had only 10 months, starting in March, with a winter period not assigned to any month. Around 713 BC, January and February were added, making 12. Later, Julius Caesar reformed the calendar in 46 BC, creating the Julian calendar with months of 30 and 31 days to match the solar year.
Names that no longer fit
The names September, October, November and December come from the Latin words for seven, eight, nine and ten, because they were the 7th to 10th months in the old Roman calendar. When January and February were added at the start of the year, these months moved but kept their names.
Did You Know?
July is named after Julius Caesar and August after the emperor Augustus. They were originally called Quintilis and Sextilis, meaning fifth and sixth.