A year is a time period, just like a second, minute, hour or day. We humans are the ones who have decided the duration or length of each of these units. Yes, there is a strong logical and astronomical connection to it.

To understand a calendar year, first we need to figure out which calendar are we referring to. Most commonly or globally we refer to the Gregorian Calendar; which is a solar calendar with 12 months of 28-31 days each. In all it comes to 365 days with a leap day being added to February in the leap years. In short a normal year has 365 days where as a leap year has 366 days. 2020 was a leap year with 366 days.

Here is the list of months with the number of days for your quick Reference:

MonthsNo. of Days in a Normal YearNo. of Days in a Leap Year

Thought bubble: If someone is born on 29th February, do they celebrate their birthday once every four years? As a child I always had this question until I met someone who was actually born on 29th Feb. and he celebrated his birthday every year. That’s correct, because every three years, he use to celebrate his birthday on March 1st and then on 29th Feb.

Another question to think is – Why does the leap day gets added in February?

Actually, the calendar year was originally meant to start in March with the vernal equinox, so that’s the first day of spring. And thus February was the last (12th) month of the year, that’s why the extra date would be added in February.

Fact Check – If February was the 12th month then January should have been 11th and December (Deca) to be 10th, November (Nova) to be 9th, October (Octa) to be 8th…which makes complete sense if we look at the Greek Numericals.

Question to explore – Why is a leap year called a ‘leap‘ year?

Clue – If your birth day was on Monday in 2018, it would have been on Tuesday in 2019 but NOT on Wednesday in 2020. Because 2020 was a leap year, it jumped (leaped) over Wednesday to make it on Thursday!

But one question remains unanswered – Why do we need a leap year?

Actually, Earth takes 365 days, 5 hours, 48 minutes, and 46 seconds to complete one revolution. So our calendar year is shorter than the actual (tropical) year by 0.2422 days (5 hrs., 48 mins. and 46 sec.). To tally the figures and make corrections, we add one day every fourth year (leap year). Thus, three calendar years are 365 days long; the fourth calendar year is 366 days long. In 1582, Pope Gregory XIII reformed the calendar by specifying that all years divisible by 4 are to be leap years except for century years, which must be divisible by 400 to be leap years.

For Example – The century year 2000 was a leap year because its divisible by 400 but the century year 2100 wont be a leap year since its not divisible by 400. Other (non-century) years like 2020 is a leap year as its divisible by 4.

Just imagine if we don’t consider the idea of correction i.e. leap year our seasons will start drifting. How would you feel to have summer in December? Thanks to leap year, our seasons will always occur when we expect them to occur, and our calendar year will match the Earth’s astronomical year.  

PS: This post is dedicated to my students from Grade 6.