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Monday, February 29, 2016

What is a Leap Year?

Year 2016 is a Leap Year, meaning there is an additional day every four (4) years and in the month of February, therefore every leap year February extends until the 29th from the usual 28 days.

photo not mine. credits to owner

But why do we have Leap Years?

Let me explain, based also on my short research.


cute Google Doodle
Basically, a leap year or an additional day in a year is actually a corrective measure to synchronize the calendar year to the seasonal year.  In astronomy, a year is the Earth’s orbit period around the sun, which takes 365.25 days (31 557 600 seconds to be exact), while Gregorian calendar, our current standard calendar uses 365 days. That means Gregorian calendar falls short of .25 day, thus, to compensate the .25 day short, 1 day (equivalent to 4 of .25day) is added every 4 years to harmonize it to the Sun’s apparent position.

What would have happened if we have continued using the 365 days only all throughout? Well, the seasons will also change in the future. There will come a time that summer will probably fall in December, and winter in June or July, days and seasons will fall out of sync.

Therefore, a leap year has 366 days and February 29th is called the leap day just like today.

photo not mine. credit to owner

Why of all the months in the year, February is the chosen one where a leap day is added? And why does February only have 28 days during the common year?

Some say that, February was originally has 29 days and Augustus Ceasar took one day and added it to Sextilis to make it 31 days and changed the name of the month into Augustus. I think this is only a myth since I haven’t found any written facts while doing this short period of research.

According to history, the Roman Calendar originally have 10 months only starting from March to December, with 4 months of 31 days and 6 months of 30 days, a total of 304 days.

Martius: 31 days
Aprilius: 30 days

Maius: 31 days

Junius: 30 days
Quintilis: 31 days
Sextilis: 30 days
September: 30 days
October: 31 days
November: 30 days
December: 30 days


The rest of the day after the end of December and before the beginning of Martius were neglected because it was a non-productive days thus, were not assigned to any months.

During the Numa Pompilius time, the calendar was reformed. Even numbers were considered unlucky so Numa took 1 day from each of the 6 months and added it to the 51 unassigned winter days, totalling to 57 days. These 57 days were divided into two months January to 29 days and February by 28 days.

Ianuarius: 29 days
Februarius: 28 days

Martius: 31 days
Aprilius: 29 days

Maius: 31 days

Iunius: 29 days
Quintilis: 31 days
Sextilis: 29 days
September: 29 days
October: 31 days
November: 29 days
December: 29 days


To sum it up, there were only a total of 355 days. Even with the addition there were still ten (10) days short and became out of sync with the solar year.

Fast forward to 46BC, the Roman calendar was reformed under the rule of Julius Ceasar. The first step was to start the year in January 1, and extended the number of days to 445 days to compensate the unsynchronized years. Thus, 46 BC was considered the longest year, the last of the series of irregular years and the “last year of confusion”.

The new Julian calendar took effect on 45 BC. Ten (10) days were added to the pre-Julian calendar of 355 days, 2 days added in January, Sextilis and December. One (1) day each in April, Junius (June), September and November. February still has 28 days in common years and an extra day added during leap year.

Romans later on renamed the month Quintilis to Iulius (July) after Julius Ceasar in 44BC and Augustus (August) for Sextilis after Augustus in 8 BC.

Fast forward again, today, Gregorian calendar, also known as the western calendar is the mostly used calendar, though there are still using other forms of calendars in other countries. It is already a refined Julian calendar introduced by Pope Gregory XIII on October 1582.


This is quite a long and hurry post just to catch up with the Leap Day 2016. I do hope you, learn something here. Ciao! J