Why is the solar calendar in February only 28 or 29 days?

Have you ever wondered why February has 28 days (or 29 days if it's a leap year) yet? If you know this truth, you will be surprised!

Archaeological experts have discovered the reason for this is the former retention of the Roman calendar. The original Roman calendar was issued by Romulus, the first emperor of Rome. His calendar is based on the Moon's cycle , which is similar to the Lunar calendar of the Eastern people, but only 10 months starting in March and ending at the end of December according to the list below. This January and February never existed:

Note: the numbering of January, 2, 3, . is due to the translation of Vietnamese people, while in the original of the Roman calendar as well as the translation of many languages ​​in the world, each month has its own name as above.

Thus, a year has only 10 months equivalent to 304 days, ie there is a two-cycle period of the Moon not included in the calendar. The cause of this problem stems from the fact that the Romans did not have a winter concept in the daily calendar because in their opinion the winter was the most useless time for agricultural cultivation.

February was then considered the last month of the year instead of the current convention of December.

Around the 8th century BC - in particular 731 BC, Numa emperor Pompilius realized this was silly and he decided to add another two months to the schedule for the full 12 cycles of the Moon. Each month has 28 days, making the lunar calendar full 12 cycles of the Moon, a total of 354 days with the arrival of January and February. Because these new 2 months are "late birth" , February was then considered the last month of the year instead of the current convention of December.

However, the concept back then specified even numbers related to bad luck, so Numa Pompilius decided to increase by 1 day to the total number of days in five odd numbers. Besides, the number of days of the month is also adjusted to an odd number, but if so, the number of days in the year will be an even number again. Finally, Emperor Pompilus decided to choose the last month of the year - February - which will be 28 days as the list below because he thinks that if there must be an even number of days, choose the shortest month:

However, the lunar calendar of the Moon gradually reveals weaknesses, it does not properly reflect the cycle of changing weather seasons, because this cycle is associated with the Earth's movement around the Sun, not must move the Face around the Earth. For that reason, the Romans decided to add one leap month every 27 days after February 23, named Mercedonius (only 23 days in February).

As a result, changes like this make scheduling troublesome. By about 45 BC, Emperor Julius Caesar decided to change this calendar, keeping it for 12 months but adding days in months so that the 12 months coincided with the Sun's cycle (the Sun's location cycle in the sky, not the Earth's cycle moving around the Sun because at that time people didn't know Earth had orbit around the Sun.)

The calendar we use today is the Roman calendar that has been further refined.

In addition, the Caesar emperor also set the rule that every four years, February would be added one day to match the Sun's cycle when it was calculated at 365.25 days, which is basically quite close to the real cycle of the Earth around the current Sun we know is 365.2425 days. In fact, right after changing the calendar, in 46 BC - the first year applied the new calendar - there were 455 days.

There is a source of documents that originally stated in Caesar's calendar, February has 29 days and every 4 years it is added one day to 30 days, ie there is no big difference with other months. However, later when the months were renamed, the 29th day of February was transferred to August because the English name was August - it was named after Augustus (Emperor founded the Roman empire) - to for that month the length of the month of July (July) is named after Julius Caesar.

The calendar we use today is the Roman calendar that has been further refined. The division of months remains the same to respect history and that's why there are fewer days in February than the other months. Basically this is just a convention, does not affect the use of human time.