Leap Year!!! No chord for Feb 29th — Sorry, but we need a chord every day of the year not every four years.. Take a day off and review all the previous chords for January and February.

Why Do We Have Leap Year?

A leap year (or intercalary or bissextile year) is a year containing one additional day (or, in the case of lunisolar calendars, a month) in order to keep the calendar year synchronized with the astronomical or seasonal year. Because seasons and astronomical events do not repeat in a whole number of days, calendars that have the same number of days in each year, over time, drift with respect to the event that the year is supposed to track. By inserting (or intercalating) an additional day or month into the year, the drift can be corrected. A year that is not a leap year is called a common year.

In the Gregorian calendar, a year ending in "00" that is divisible by 400 is a century leap year (2000 was a century year), with the intercalation of February 29 yielding 366 days instead of 365. Century years (divisible by 100) that are not divisible by 400 are not leap years but common years of 365 days. For example, the years 1600, 2000, and 2400 are century leap years since those numbers are divisible by 400, while 1700, 1800, 1900, 2100, 2200, and 2300 are exceptional common years despite being divisible by 4. Leap years divisible by 400 always start on a Saturday; thus the leap day February 29 in those years always falls on a Tuesday (dominical letter BA)