Interkalointiprosessija

Interkalointiprosessija is a term that refers to the process of inserting an additional day into a calendar year to synchronize the calendar with the solar year. This practice is primarily observed in the Gregorian calendar, which is the most widely used calendar system globally. The term "interkalointiprosessija" is derived from the Latin words "intercalare," meaning "to insert," and "dies," meaning "day."

The need for an interkalointiprosessija arises because the Earth's orbit around the Sun takes approximately 365.2422 days, which is not an exact number of days. To keep the calendar year aligned with the solar year, an extra day is added approximately every four years. This additional day is known as a leap day and is inserted into the month of February, making it 29 days long.

The rule for determining a leap year is as follows: a year is a leap year if it is divisible by 4, except for end-of-century years, which must be divisible by 400. This means that the year 2000 was a leap year, although 1900 was not. The interkalointiprosessija ensures that the dates of the calendar remain in sync with the seasons over time, preventing the calendar from drifting out of alignment with the solar year.