How many days are in a year?

How many days are in a year? It is one of the questions that is asked by many people now and then. The answer may seem simple i.e. 365 days per year. However, the reality is a bit more complicated. Most years do indeed have 365 days but some have 366. This is because of a leap year. It occurs every four years. During a leap year, an extra day is added to the calendar to keep it aligned with the rotation of the Earth around the sun.

The fact is that even with the addition of one extra day after every four years; our calendar is still not perfectly aligned with the solar year. By the end of this article, you’ll have a much deeper understanding of the concept of a year and how many days it has.

Understand the term “A Year”

In simple language, we can say that a year is a unit of time that is based on Earth’s rotation around the sun. More specifically, it is the time taken by the Earth to complete one orbit around the sun.

This time is approximately equal to 365.24 days/ 365 days and 6 hours. We can also define a year as a period of 12 months. There are different ways of defining these months as per various calendar systems. For example, the Gregorian calendar has 12 months with varying numbers of days like 31 days in January, 28/ 29 in February, 30 in April, etc.

A year is the most used and fundamental unit to mark the passage of long time such historical events.

The Concept of a “Day”

Just like a year, a day is also a unit to measure the time. It typically refers to the time taken by the earth to rotate on its axis. The length of a day is equal to 24 hours. An hour is further divided into 60 minutes. These smaller units are meant to measure time with greater precision and accuracy.

The length of a day can vary slightly due to several factors. These factors include the Earth’s distance from the sun, the tilt of its axis, other gravitational forces, etc. Another fact is that the length of a day can vary by up to several milliseconds over a year. However, these changes are so small we neglect them while doing our general calculations.

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Calculating the number of days in a year

The calculation behind the number of days in a year is worth understanding. It is the period for the Earth to complete one orbit around the sun. It is also called a “Tropical Year”. A tropical year is approximately 365.2422 days long. It happens because the orbit of the earth is not perfectly circular. In fact, it is elliptical in shape. Plus, the speed at which it moves around the sun is not constant.

To account for the time of 356.24-days long year, the Gregorian calendar has a year of 365 days with an extra day in the month of February every four years. This day is called a leap day.

To put it simply, we can say that a non-leap year has 365 days. On the other hand, a leap year has 366 days.

You should also note that adding an extra day is not the perfect calculation for a tropical year. The fact is that adding an extra day every four years result in a calendar year that is slightly longer than a tropical year. To compensate for it, leap years are skipped on years that are divisible by 100 but not by 400.

For example – the year 2000 was a leap year because it is divisible by both 100 and 400. But, the year 2100 will not be a leap year because it is not divisible by 400.

Explore Few Interesting Facts about Days, Years, and Calendars

The Gregorian calendar was introduced by Pope Gregory XIII in October of 1582. This calendar was designed to replace the Julian calendar.
The leap year occurs every four years. However, there are some exceptions to this rule. If the year is divisible by 100 and not divisible by 400 then it is not a leap year.
The Gregorian calendar is the most widely used calendar in the world today
Interestingly, the names of days of the week in the Gregorian calendar are taken from ancient Roman mythology. Sunday is named after the sun. Similarly, Monday is named after the moon, etc.
The calendar (Gregorian) repeats itself after 400 years.