mitmeidkuud

Mitmeidkuud (Estonian for "extra months") refer to the practice of adding one or more additional months to a calendar year, typically to account for discrepancies between the solar year and the lunar or lunisolar calendar systems. This concept is most commonly associated with certain East Asian and traditional calendars, where the lunar year is approximately 11 days shorter than the solar year. Over time, this discrepancy accumulates, leading to seasonal drift.

In lunisolar calendars, such as the Chinese, Korean, and Vietnamese calendars, an extra month (known as a "blue moon" or "intercalary month") is occasionally inserted to realign the calendar with the solar year. The decision to add a mitmeidkuud is based on astronomical observations, particularly the phases of the moon and the position of the sun relative to the vernal equinox. This ensures that important seasonal events, such as planting and harvesting, remain synchronized with natural cycles.

The process of determining when to add an extra month is complex and involves tracking lunar cycles while accounting for the solar year. Traditionally, this was done by officials or religious authorities who consulted astronomical records. In modern times, algorithms and digital tools have streamlined the calculation, though the principle remains rooted in balancing lunar and solar timekeeping.

While mitmeidkuud are most prominent in East Asian calendars, similar practices exist in other lunisolar systems, such as the Hebrew calendar, where leap months are added to maintain alignment with agricultural and religious observances. The inclusion of extra months ensures that the calendar remains practical for daily life, cultural traditions, and long-term planning.