The Effect In Time Of Leap Year

The Earth And The Sun

Every year, Earth revolves completely around the sun. Along its rotational course, the Earth drifts from time to time or season as it heads the complete revolution in the sun. Uncommon to others, the Earth completes its revolution around the sun at exactly 365.2500 days in Julian Calendar or calendar year. So, since we have only 365 days in our calendar, we neglect 1/4 day prior to leap year. As a result, an intercalary or inserted day is assigned to February every leap year to compensate the neglected but accumulated quarter day each year in common years.

The leap year also known as intercalary year creates two-day difference in a calendar. Unlike in a common year, we have only one day difference. Thence, the current day of the year will be forwarded by a day the following year in a common year. 

Common year is the year in the absence of a leap year.

For example this year, a common year, August 27, it falls on Tuesday and by next year, August 27, 2014 will expectedly fall on Wednesday. On the other hand, if there is a leap year next year, August 27, 2014 will land not on Wednesday as anticipated but rather be placed on Thursday after intercalation or insertion of February 29, 2014 (so be it).

Historical accounts about why February has only 28 days. According to other historians, there were only 10 months starting from March to December in the Roman calendar long time ago. The claim was so evident because if you can count the old calendar months starting with March to December, the months October, November, December could fall chronologically on the 8^th, 9^th and 10^th calendar month of the Romans. January and February were just an excess in the season and became the last 2 months in Roman calendar lately. Originally, January had 29 days and February had 23 days. The Romans came to a decision to rearrange the calendar and added 2 days and 5 days to January and February to start the calendar according to moon cycles.

The purpose of leap year in our lives is to align the actual year and the actual season in proper order in time and to correct the disarray of the Earth's orbit around the sun due to drifting.

Although we do not use Julian Calendar or calendar year, but the importance of leap year remains in our lives.

Additional Day Once In Every Four Years

The correction that we do from time to time using leap year is very important because if we do not correct it, expected season in a month will vary as time goes by. You can expect snow in mid-year or summer in January. What a big mess in our actual year if we could just ignore the imbalances and slight difference in time in the Earth's complete revolution in the sun.

Still, many are confused about the difference between rotation and revolution. Rotation is the movement of the Earth on its axis. That’s why we experience night and day within 24 hours everyday. Revolution is the complete rotation of Earth around the sun and it takes a debatable 365 days to make it.

The Leap Year Founder: Julius Caesar

Now, Earth takes absolutely 365.2422 days to make a complete revolution around the sun in a year with exception. This is called the actual year or tropical year. In other words, the 365 days we use every year is still short of 0.2422 days and can be translated in 5 hours, 48 minutes and 46 seconds short of the actual year. So if we ignore that 0.2422 days in 4 years, we shall lose 1 day in our calendar day or 25 days in 100 years. Whoah! That’s a big mess. Thanks to Julius Caesar for inventing leap year to correct mistakes in our season.

In comparison, Julian calendar, with 365.2500 days in a year without exception and better than mere 365 days, has still a slight difference compared to the actual year computation above. In contrary, Julian calendar accumulates additional one day every 128 years. As a consequence, he added additional 81 days to correct their calendar and introduced the Julian Calendar too. That's the reason why the leap year was credited to Julius Caesar, as advised by astronomer Sosigenes under the proposal of the former, who found the date of spring equinox behindhand by 81 days and reformed calendaring to balance the season.

By 1582 AD, the difference between the calendar year (Julian) 365.2500 days and actual year 365. 2427 days accumulated by 10 days causing error to the Easter season and alarm to the Pope. Thus, on February 24, 1582, Pope Gregory XIII issued a Papal Bull known as Inter Gravissimas (in the gravest concern) Order: First, to reset the start of the year by institutionalizing the Gregorian Calendar and by ignoring October 5-14 or equivalent to 10 days on that year to bring back the vernal equinox on March 21 in Northern Hemisphere. Secondly, to bring the year closer to 365.2422 days or tropical year equivalent to Earth's revolution in the sun.