# Why are there leap years and what are they

When we are asked how many days a year has, the most common is to answer 365. However, there are situations in which this figure is not always the case. In fact, every four years, we find years that have 366 days. They are known as leap years that, although they are very similar to common years, have a series of particular characteristics that make them different from other years.

## What are leap years

**Leap years** are characterized by being years in which instead of 365 days there are **366 days** . In other words, these years have **one day more than the rest of the years** . This day is always placed on the same date, which makes it easier to post and manage them. This day is February **29** . As everyone knows, the usual month of February has 28 days (which makes it the shortest month of the year, since the rest of the months always have 30 or 31 days depending on the case). This explains why it is the month of February, and not any other, to which this extra day typical of leap years is added, since it allows a greater balance to be maintained between all months of the year.

Beyond the fact that the month of February has one more day, there is no characteristic that makes leap years different from the rest of the usual years. Thus, if it weren’t for this extra day on February 29, a leap year would be absolutely the same as any other year.

If a leap year is exactly the same as any other common year, then why is there a need to make these years exist? Wouldn’t it be more convenient to make all the years the same? The answer is no, since when we say that a calendar year has 365 days, we are giving an insufficient answer. Actually, the correct thing to say is that **a year has 365 days and 6 hours** . Thus, there are 6 hours each year that do not correspond to a full day. However, even though they do not correspond to any year, those hours do accumulate.

The problem with this “extra” time is that, if it is not counted, the hours and days would be out of balance, which would make the seasons and the day and night cycle not in line with reality. Consequently and to avoid it, what is done is to add those 6 hours of each year until they give a full day. That is, **every 4 years, a whole day or 24 hours has been completed** . This day is artificially introduced into the normal calendar, allowing the cycles of hours and day and night to adjust again to reality and nature.

This artificial day that is added is the aforementioned **February 29** . Due to the fact that the remaining hours corresponding to each year that are accumulated are 6, and that a day on Earth has 24 hours, this artificial day must be introduced every 4 years. For this reason, we find that the cycle of the years is 3 normal years and 1 leap. Once this cycle is completed, the three normals are resumed and then the leap is entered again, and so on cyclically.

The choice of leap years is an artifact of the calendar. Actually, it could be calculated in different ways. However, its placement comes from the times of **Julius Caesar, the Roman emperor who modified the calendar** of the time to adjust to leap years and correct this lag between 365 days a year and the remaining 6 extra hours. Later, this calendar was perfected by **Pope Gregory XIII** , an event that causes the calendar we use today to be called the **Gregorian calendar** .

Taking this tradition, leap years have been happening every four years to this day. Thus, 2016 was a leap year. This year should be followed by three normal years (2017, 2018 and 2019). This is followed by a new leap year that will correct the 6 o’clock lag. In other words, **the year 2020** will be a leap year. Then there will be another three normal years (2021, 2022 and 2023) to finally have a new leap year (2024). And so on.