Why February has 28 days? Brief Explanation

Why February has 28 days, why it becomes 29 after every 4 years. and What is the leap year? These questions must have come to your mind,

It takes 24.0000006 Hours to complete a day, therefore it takes 365.25 days to complete a year. For better understanding, we have to understand What is a day?

What is a Day?

you probably love to watch stars time-lapse videos but as a matter of fact. Our earth is moving instead of the stars., Our day depends on our nearest star. Example, The Sun.  The earth moves in a counterclockwise direction. & revolves around the sun in a counter-clockwise. That's because a day becomes day and night. One day happens when earth completes a cycle.  Earth takes 23.9 hours to rotate in its distance, this is called sidereal Day. When earth completes a  cycle in orbit. 
Then it needs to be a little bit more to get on the same point &  and this called solar day.

So, now we got the fact that Sidereal day is 23.9 hours long &  Solar day is 24.0000006 hours long. & truly solar day is considered to a day. And solar watch tells us the true time instead of regular watches.

24 hours were kept in a single day as an around figure, & this belongs to the Roman calendar, In Ancient civilization, there were 10 months in a year, which were from March to December which makes 304 days in a year, in the period of Jan to Feb time they used to do nothing, just because of  winter conditions, & that is why these two months were considered as abominable.
Due to leaving so many days on a scale, it took a huge difference. At the moment, Roman emperor announced that the two months will be added to the year then Jan and Feb got added in the last & Considered them 11th and 12th month of the year. after the calculation, the remaining days were kept in Feb. which were 28.

But our Question remains same, Why after every 4 years, an additional day is added to the year.?

Lets back to the Solar Day for better understanding. Solar Day takes 24.0000006 Hours to complete a single day & this makes 365.25 Days in a year, When this .25 day  ( .25+ .25+ .25+ .25 = 1 ) becomes 1 day right after 4 years, this day gets added in February & this process makes 29 Days also known as LEAP YEAR, Probably, this would be a precious day who have born on this day. Isn't?

This Correction has been done by Roman emperor Julius Caesar in Julian Calendar in about 46 BC. In this calendar, January and February were placed first in the sequence of the months.

But it also had a decline...

Calendar adds a little bit when adding a single day to the Leap Year Because that does not take exactly 365.25 Days But take 365.2421891 Days (you may cursing me but that's true). In 1582 Julian Calendar was going 10 days ahead. Difference happened on Easter due to this. therefore, On 4 Oct 1582, Pope Gregory XIII correct this error which is known as the Gregorian Calendar. To revive the misplacement of 10 days, He proposed on 4 Oct 1582, that tomorrow will be the 15th of Oct instead of 5th Oct. & this is the Calendar we are using now.!

ERROR

In Julian Calendar, there was an error that after every 400 Years 3 days gets added.

OUTLOOK

This probably along but must be an interesting fact, we got to knew the way, why February has 28 Days right after 4 years hopefully you guys got to know nicely, Is there anyone here whose birthday is on 29 Feb?? Let me know inside the comment section.