The years 2012 and 2016 are examples of leap years. This means that in both there are a total of 366 days and not the usual 365. The variation of one day in leap years occurs in the calendar on a specific day: February 29th. Obviously this change in the total number of days has a plausible explanation.
What is a leap year and why do they exist?
To understand this peculiarity of the calendar, we must remember that the Earth moves around the Sun and the complete orbit takes place in 365 days and 6 hours. This figure makes the year last 365 days, but there is a problem with the remaining 6 hours. Because of the time that the Earth’s movement around the Sun reaches and to coincide with the calendar time, the leap year was created.
Thus, every four years, there is a leap year (3 successive years with 365 days and the fourth recovering the remaining hours, making the year with 366 days). If you could not add a full day every four years, the seasons would uncompensated in relation to the calendar, so that after 700 years the Christmas in the northern hemisphere would be in the summer and the opposite happens in the southern hemisphere. Leap Year
The origin of our calendar
Primitive peoples used the phases of the Moon as a calendar. This idea was rejected when the Egyptians discovered that lunar calendars were not used to predict the beginning of the annual floods of the Nile River. This is because the phases of the Moon are very short and make mistakes more easily.
On the other hand, the Egyptians realized that following the movement of the Sun they could predict the seasons and, in addition, every 365 days arrived the longest day of the year. Since then, the Egyptians started using the solar calendar. This conception of the Egyptians was incorporated by the Romans.
Julius Caesar was the emperor who definitely renewed the calendar and introduced the leap year concept
This happened in the 1st century BC. C, as before the Romans had only a 10-month annual schedule.
The calendar introduced by Julius Caesar is known as the Julian calendar, which was reformed in the 16th century, at the initiative of Pope Gregory XIII and is therefore known as the Gregorian calendar. The Gregorian calendar introduced a modification regarding leap years, so this new norm incorporated some exceptions to the general criterion of leap years. This adjustment was based on new knowledge about the Earth’s translation around the Sun. Leap Year