Life has been so busy lately that it was almost lost to me that 2016 is a leap year! For many people that only means another day to wait for their paycheck or one more day of putting their nose to the grind at the work to finish a big project. For me, it enabled me to squeeze out one more day at the gym before my physical fitness test. My job requires that I maintain a high level of physical fitness which is tested regularly throughout the year. To make this one special, I decided that I would take it on leap day. And, since this is a chess blog and chess players (typically) enjoy odd facts and history, I thought it would be nice to look into the origins of February 29th. Plus, it gave me a reason to post today…

An Imperfect Path Around the Sun

There have been many calendars throughout history including the Lunar, Julian, and the Gregorian Calendars. Most of us learn very early in school that the Earth orbits the Sun in a semi-perfect circle. Typically we celebrate a new year around the world every 365 days, but scientists observed that during the use of the old Lunar Calendar that seasons would shift drastically over time. This indicated that the calendar’s basic system for tracking the length of time it took for the Earth to orbit the Sun was inaccurate. Can you imagine having a snowstorm in Texas in July? If we still used the Julian Calendar, it is highly likely.

It takes the Earth on average, approximately 365 days, 5 hours, 48 minutes and 45 seconds long (365.242189 days) to complete one full orbit around the Sun.1 To compensate for this seasonal shift, it was determined that an extra day was needed every so often to balance out the inaccuracy of the calendar. Julius Caesar’s Julian Calendar introduced the concept of the leap year, but its calculations were still not enough to compensate for the full effect of the uneven orbit. This was because the only rule used to calculate the need for a leap year was that the year had to be evenly divisible by four.

Here are some interesting facts about the error rates in our common, Western calendars:

  • 365-day Calendar (with no leap years calculated).
    • Length: 365 Days
    • Error Value: 6 hours/year (1 day in 4 years).
  • Julian Calendar
    • Length: 365.25 Days
    • Error Value: 11 min/year (1 day in 128 years).
  • Gregorian Calendar
    • Length: 365.2425 Days
    • Error Value: 27 sec/year (1 day in 3236 years).
  • Mayan Calendar <– not saying it was aliens, but…
    • Length: 365.242036 Days
    • Error Value: 13 sec/year (1 day in 6500 years).


Did the Mayans know something we don’t? As some ancient astronaut theorists believe…
(hope you read that in the guy’s voice)

The Vatican Steps In

Pope Gregory XIII realized the problems with the Julian Calendar and comissioned a new calendar to be created that would fix the leap year issues. The result was a calendar adopted in 1582 in Italy, Poland, Portugal, and Spain known as the Gregorian Calendar. It is the most widely used calendar in the world today. Here are some specifics:

  • The Gregorian Calendar is a 365-day, solar calendar divided into 12 months of irregular lengths.
  • 11 of the months have 30 or 31 days, while February has only 28 days during a common year.
  • Nearly every four years is a leap year where one extra day is added to February (which is today), making the calendar 366 days long.
  • The formula for calculating leap days is much more complex than the old Julian Calendar, which makes the Gregorian Calendar far more accurate.
    1. The year is evenly divisble by 4.
    2. If the year can be evenly divided by 100, it is NOT a leap year, unless (see third rule)
    3. The year is also evenly divisible by 400.


An Early Example of the Gregorian Calendar (Credit: ScienceSource)

So, campers! Enjoy this extra day because it only comes around so often! Kiss your girl (or guy), phone a friend, play some chess, and enjoy it because you can bet that summer will be arriving at the same time it did last year thanks to the hard work of the people who watched the skies throughout history and helped us create one of the most essential tools in existence: our calendar.


  1. “Julian Calendar,” Time and, accessed February 28, 2016,