This year marks the calendar with an extra day in February. The last leap year was 2008. Run by a complicated formula which says leaps only occur every 4 years as long as the year isn’t exactly divisible by 100, but any century year which is exactly divisible by 400 are still leap years. 1900 wasn’t a leap year because it couldn’t be divided exactly by 400 however the year 2000 was and so it had a leap day; got that?
The calendar we use in western culture is referred to as the Gregorian Calendar. Pope Gregory XIII introduced the calendar which was named by a decree signed on February 24 1582; the decree is known as a a papal bull. The reformed calendar was adopted after the somewhat less accurate Julian calendar; a calendar which gained about three days every four centuries compared to the observed equinox times and the seasons. This was of course of monumental importance because we all know what sticklers for time Romans are. It has been said centuries later their descendent’s were thus able to keep the trains running on time.
The Chinese recognized bull when they heard it, papal or otherwise and use a lunisolar1 calendar. This calendar is used in many cultures whose date indicates both the moon phase and the time of the solar year. The Chinese leap year has 13 months, with a leap month added about every 3 years. The name of a leap month is the same as the previous lunar month. The leap month’s place in the The Chinese calendar varies from year to year. Unlike the Gregorian calendar, 2006 was a leap year in the Chinese calendar.
Now that you know all of that, you might consider using the extra day to plan or take time with friends or family. Enjoy!
1 – In a lunisolar calendar; if the solar year is defined as a tropical year3 then a lunisolar calendar will indicate the season; if it is taken as a sidereal year2 then the calendar will predict the constellation near which the full moon may occur. Usually there is an additional requirement the year have a whole number of months, in which case most years have twelve months but the leap year has thirteen.
2 – A sidereal year is the time taken by the Earth to orbit the Sun once with respect to the fixed stars. It is also the time taken for the Sun to return to the same position with respect to the fixed stars after traveling once around the ecliptic.
3 – Astronomers have progressively refined the definition of the tropical year, and currently define it as the time required for the mean Sun’s tropical longitude (longitudinal position along the ecliptic relative to its position at the vernal equinox) to increase by 360 degrees (that is, to complete one full seasonal circuit).