# What is leap year? Easy way to calculate leap years

You all probably know or have heard of leap years and how to calculate leap years somewhere, but what exactly are lunar and lunar year leaks for? And how to calculate the leap year is the most correct, you do not know clearly.

Today’s article below I share is an additional synthesis article to clarify those things. ## 1. What is leap year?

Leap years are those with 366 days (solar calendar)
Every 4 consecutive years of tourism, there will be a 366-day year, called a leap year.

A calendar that calculates time according to the sun is called a solar calendar. That’s when the Earth rotates around the sun for 365 days 6 hours. The calendar year has an integer number of 365 days. Thus, a calendar year has 6 hours leftover and if 4 years accumulated, there will be 24 hours, corresponding to one day. The leap day or many places called the solar day according to the convention that has 29 days in February, then February 29th is called the day of leap days; in years of 356 days, February has 28 days.

The moon’s time calendar is called the lunar calendar. Moon month averages 29.5 days. A lunar year has 354 days, it’s shorter than the calendar year by 11 days. So every 3 years is shorter than 33 days (more than 1 month).

In order for the lunar calendar to be just a moon phase, and not much different from the weather of the four seasons, one must give a leap month every 3 years so that the lunar year and the solar calendar are not much different. However, this is not enough, the lunar year is still slower than the calendar year. People remedy this situation by being every 19 years once every 2 years and a leap month.

In 19 calendar years, there are 228 calendar months, corresponding to 235 lunar months, 7 months over the calendar year, called 7 leap months. The previous seven months are conventionally applied for the 3rd, 6th, 9th or 8th, 11, 14, 17 and 19 years of the 19 year cycle.

## 2. How to calculate the solar calendar year and the leap day?

The calculation of the solar year (DL) and the lunar year (AL) is not very complicated, but calculating the leap month of the AL year is very complicated.
By convention, if any calendar year is divisible by 4, then that year is a leap year.
For example:
2019 is not divisible by 4 so 2019 is not a leap year.
2020 is divisible by 4 so 2020 is a leap year.

In addition, for years with full-century years (years with the last two digits being zero), you divide the number of years by 400, and if you divide by that number, that year is a profitable year (or the first two digits of the year are divisible by 4).

For example, 1600 and 2000 are leap years but 1700, 1800 and 1900 are not leap years.

Similarly, 2100, 2200, 2300, 2500, 2600, 2700, 2900 and 3000 are not leap years.
but 2400 and 2800 are leap years.

In the solar calendar year there will be one more day.
Leap days will be February 29th of the calendar year

## 3. How to calculate lunar year and leap month?

Take the number of corresponding calendar years divided by 19, if the remainder is one of the numbers: 0; 3; 6; 9 or 11; 14; 17, the lunar year has a leap month.
For example:

2014 is the lunar year (one more month) because 2014 divided by 19 balances is 0.

2015 is not a lunar year because 2015 is divided by 19 surplus 1.

2016 is not a lunar year because 2016 is divided by 19 surplus 2.

2017 is the lunar year because 2017 divided by 19 remainder 3.

2019 is not a lunar year because 2019 is divided by 19.

2020 is a lunar year because 2020 is divided by 19 remainder 6.
In the lunar calendar, the leap year will add one month, which means there will be 13 months in the year.
As a rule, the lunar calendar is only 12 months so the leap year will have 2 consecutive months, consecutive months will.

Table of leap years and leap months of lunar calendar:

The conclusion is that the leap year is just a tactic of the calendar makers to make the lunar calendar and the solar calendar not much different, without any implications on the weather and climate.