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Leap Day - A Quadrennial Quirk Of The Calendar
February 29, 2024 at 10:16 AM EST
By WeatherBug Sr. Meteorologist, Julie Gaddy
Throughout civilization, calendars have been devised to track the passing of time and seasons.
The Gregorian calendar is the most widely used calendar throughout the world today. Enacted in 1582 during the time of Pope Gregory XIII, this calendar is based on the amount of time it takes the earth to complete one revolution around the sun, thus making it a solar calendar.
By tracking the relationship between the earth and sun on the vernal equinox (first day of Spring), the number of days in a year was calculated to be 365.2425 days or 365 days and just under 6 hours. This was a slight revision of the Julian calendar, which had a slightly longer year.
The Julian calendar had been widely used in Europe and North Africa since its inception in 45 BC. Julius Caesar worked with astronomers of his time to determine a standard calendar for use in the Roman Empire. The names of the months retain their Roman roots to this day.
A normal year contains 365 days. When the year is divisible by four, as is 2024, an extra day is added to the calendar to compensate for the extra 24 hour observed over the previous 4 years. The exception to this rule is for century years not evenly divisible by 400, such as 1900 and 2100. February 29 became known as the official Leap Day during the late Middle Ages.
Meteorological data are recorded on Leap Day just like any other day. Thunderstorms are pretty rare in Chicago during the month of February, but they happened on Leap Day in 1976. What about normal highs and lows? When computing daily normals, February 29 is assigned the same values as February 28.
The Gregorian calendar is the most widely used calendar throughout the world today. Enacted in 1582 during the time of Pope Gregory XIII, this calendar is based on the amount of time it takes the earth to complete one revolution around the sun, thus making it a solar calendar.
By tracking the relationship between the earth and sun on the vernal equinox (first day of Spring), the number of days in a year was calculated to be 365.2425 days or 365 days and just under 6 hours. This was a slight revision of the Julian calendar, which had a slightly longer year.
The Julian calendar had been widely used in Europe and North Africa since its inception in 45 BC. Julius Caesar worked with astronomers of his time to determine a standard calendar for use in the Roman Empire. The names of the months retain their Roman roots to this day.
A normal year contains 365 days. When the year is divisible by four, as is 2024, an extra day is added to the calendar to compensate for the extra 24 hour observed over the previous 4 years. The exception to this rule is for century years not evenly divisible by 400, such as 1900 and 2100. February 29 became known as the official Leap Day during the late Middle Ages.
Meteorological data are recorded on Leap Day just like any other day. Thunderstorms are pretty rare in Chicago during the month of February, but they happened on Leap Day in 1976. What about normal highs and lows? When computing daily normals, February 29 is assigned the same values as February 28.