The Messy History of Our Modern, Western Calendar

For something that’s meant to lend order to our lives, the modern Western calendar has a messy history. The mess, in part, comes about because of the difficulty of co-ordinating the orbits of celestial bodies with the cycles of day and night, and the passage of the seasons.

Ancient calendars from Mesopotamia, for example, co-ordinated months and seasons by adding extra months every now and then, a process called intercalation. In some lunar systems, though, the months can wander through the seasons – this is the case for the Islamic Hijri calendar.

The solar calendar of ancient Rome gives rise to our modern Western calendar. The Julian calendar, named after Julius Caesar’s reforms of 46/45 BCE, approximated the solar year to 365.25 days and inserted an extra day each four years. That left a rather annoying 11 and a bit minutes unaccounted for. More on those minutes later.

The Julian calendar also left us a legacy of months in strange positions. Our eleventh month, November, derives from the Latin for the number nine, a result of moving the start of the year from March to January.

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