Is 1980 a leap year or a common one? Does it have 365 or 366 days? What is a leap year? The algorithm and steps to calculate

1980: Is it a leap year or a common one?

The leap year algorithm. The three conditions to check in order to know whether a year is a leap or a common one.

1) A leap year is divisible by 4 (evenly divided by 4, having a zero remainder when divided by 4):

1980 is evenly divisible by 4.


2) Except if it's divisible by 100 (evenly divided by 100, having a zero remainder when divided by 100) then it isn't a leap year:

1980 is not evenly divisible by 100.


We could have stopped at this step.

Our year is a leap year and not a common one.

It does not meet this condition.


3) But even for the previous step above, if it's also divisible by 400 (evenly divided by 400, having a zero remainder when divided by 400) then it's a leap year:

1980 is not evenly divisible by 400.


1980 is a leap year.
The last leap year before 1980: 1976.
The next leap year after 1980: 1984.

1) Each year that is divisible by 4 (divided evenly by 4, having a zero remainder when divided by 4) is a leap year... 2) Unless it is also divisible by 100... 3) But even in this last case, if it is divisible by 400, then it is a leap year. A maximum of three steps to check, in this order.


What is a leap year?

1980, being a leap year has 366 days.
A common year has 365.

In a leap year month February has 29 days.
February 29th, 1980 is a valid date.

In a common year month February has 28 days.
February 29th does not exist.


How often do the leap years occur?

Nearly once every four years is a leap year. More exactly, leap years occur 97 times in every cycle of 400 years.

Why do we need leap years in our calendar?

Leap years keep the calendar year in sync with the astronomical year, preventing us, for example, from celebrating Christmas in the month of November.

Note

The first year in the actual calendar (also called Gregorian, modern, civil) was 1582. Before this year another calendar (Julian) was in use, with different rules. Not all the countries adopted the Gregorian calendar at the same time, in 1582. The adoption process took hundreds of years and is not even now complete. The actual calendar (also called Gregorian, modern, civil) will get out of sync by 1 day with the astronomical calendar around the year of 4818 (after ≈ 3236 of years from its creation in 1582).


More operations of this kind:

The last leap year before 1980: 1976.

The next leap year after 1980: 1984.

Is it a leap year? Last leap year before & next leap year after this year

The leap year algorithm. The three conditions to check in order to know whether a year is a leap or a common one:

1) A leap year is divisible by 4 (evenly divided by 4, having a zero remainder when divided by 4)

2) Except if it's divisible by 100 (evenly divided by 100, having a zero remainder when divided by 100) then it isn't a leap year

3) But even for the previous step above, if it's also divisible by 400 (evenly divided by 400, having a zero remainder when divided by 400) then it's a leap year

Latest checked up years / leap or common years?

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All users checked up years / leap or common

Leap Years. Common Years. What are they and why do we need them? The leap years algorithm.

What is a leap year? What is a common year?

A leap year contains 1 extra day, February 29th, over an ordinary year, 366 vs. 365.

How often do the leap years occur in the calendar?

Nearly once every four years, 97 leap years at every 400 years.

Why do we need leap years?

They keep the calendar year synchronized with the astronomical year, preventing us, for example, from celebrating Christmas in November.

Leap years algorithm.

Every year that is evenly divisible by 4 is a leap year, except for years that are evenly divisible by 100, but these years are leap years if they are evenly divisible by 400:

Examples of leap years.

  • Leap years multiples of 4 but not of 100 nor of 400: 1992, 1996, 2004, 2008, 2012, 2016, 2020, 2024, 2028;
  • Common years (NOT LEAP YEARS) multiples of 100, but not of 400: 1700, 1800, 1900, 2100, 2200, 2300;
  • Leap years multiples of 400: 1600, 2000, 2400.

Articles on the leap years

What is a leap year? What is a common year?

How often do the leap years occur in the calendar?

Why do we need leap years?

Leap years algorithm. Examples.

When did the leap year originate?

The modern (Gregorian) calendar and the Julian one. Julian calendar adjustment

How accurate is the Gregorian calendar, based on the leap year algorithm?


See all the articles about leap years above grouped together as a single article.


List of all the leap years between 1582 and 4818.


Is it a leap year? Calculate.