Leap Year

Introduction
In The Stone Age there was really no need to know when season were, for if ye wanted food, then thou shalt go and get it, whether by hunter or gathering. But when The Neolithic Revolution began, a need to track seasons was crucial. Knowing when to plant seeds and when they would be ready to harvest was extremely important to the survival of mankind in the beginnings on dormant settlements and civilizations. 
The Lunar Calendar
One of the original calendars in The World is the lunar calendar. The Lunar calendar is based off the moon. The month on a lunar calendar is similar to today's months (which are based off the moon cycle) which were 29-30 days per month. A year on The Lunar Calendar was 354 Days. The problem with this was that every year, the the start and final dates would drift 11 days.
The Julian Calendar
The Julian Calendar was a Solar Calendar. The Solar Calendar is based off the revolution of the Earth around The Sun. The Julian Calendar was invented by Julius Caesar as a reform to The Traditional Roman Calendar. It went into effect on January 1st, 45 B.C. (709 AUC). THe Julian Calendar consisted of 355 Days and 12 Months with some years having from 377 to 378 days a years to make up for decimal timing. This lead to a very disorganized system of mapping seasons and days. This mess of mapping would not last long however and in 1582, that would all change and we would see what we use in Today's World. 
The Gregorian Calendar
In October of 1582, The Gregorian Calendar, named after Pope Gregory XIII, which invented. This is the calendar most nations in Today's World use. It has 365 days and 12 months, with every 4 years, having a leap day with that year being called a leap year. This is because on this day of February 29th, is the extra day added every 4 years to make up for decimal timing over the years. This gives a leap year 366 days as opposed to 365 days on a normal year. This is a large improvement over the previous calendars, for now we only need to add a single day every four years to make up for lost time. One day however, this leap day will no longer be needed, for one day the revolution around The Sun will equal an exact 365 days every time. But for now, this is the best that we use and it is here to stay for a good while. 
Conclusion
Things change overtime. We as humans went through many different types of imperfect calendars in the past. Our calendars today are not even perfect. This is why every four years we add an extra day in February to make up for the inaccuracy. Hence the reason for the leap year. In every aspect of life, one must continue to adapt and improve; for if ye are not moving forward, than thou art moving backwards.