Keliamos

Keliamos, also known as leap years, are years that contain an extra day, February 29th, to keep the calendar year synchronized with the astronomical or seasonal year. The term "keliamos" is derived from the Lithuanian word for "leap," reflecting the practice's origin in the Baltic region. The concept of leap years is based on the fact that the Earth's orbit around the Sun takes approximately 365.2422 days, not the whole number of 365 days that is used in the Gregorian calendar.

The need for leap years arises because the Gregorian calendar, which is the most widely used calendar today, has 365 days in a common year and 366 days in a leap year. This adjustment is necessary to prevent the calendar from drifting out of sync with the seasons over time. In the Gregorian calendar, a leap year occurs:

1. Every year that is evenly divisible by 4;

2. Except for years that are evenly divisible by 100;

3. Unless the year is also evenly divisible by 400.

For example, the year 2000 was a leap year because it is divisible by 400, while the year 1900 was not a leap year because it is divisible by 100 but not by 400. The introduction of leap years was first proposed by the Roman astronomer Sosigenes of Alexandria in the 2nd century AD, but the modern leap year system was established by the Gregorian calendar reform in 1582.

Leap years have significant cultural and historical importance. In many cultures, February 29th is considered a day of good luck and is associated with various traditions and celebrations. For instance, in some countries, it is customary to propose marriage on February 29th, as the proposal is considered to have more significance than one made on a regular day. Additionally, leap years have been the subject of various myths and legends, including the belief that a person born on February 29th only has a birthday every four years.