The first near-exact measurement of a year was first introduced by the ancient Egyptians. The reference of their measurement started with a monthly lunar calendar which is based on the appearance of the new moon which coincides to every twenty-ninth and thirtieth days. But this lunar-based calendar was not very accurate.
The ancient Romans also developed a lunar-based calendar. But to make it coincide with the solar year, they added some extra months whenever they are needed to. And in the reign of Julius Caesar, he had adopted a new calendar which is based on a solar year of 365 ¼days. This become the Gregorian calendar as we known it today. Many changes were made in the number of days in a month to make this calendar right. After which, this calendar is much accurate compared to the Egyptians.
Some of the major changes made by Caesar and other Roman Emperors in the days of each month are as follows:
- The month of January was originally the eleventh month of the year having 29 days. Julius Caesar made this the first month of the year and added 2 days to make it 31 days.
- February had 29 days to which one day is added during leap years. Emperor Augustus then remove one day to February and added it to the month of August.
- March has always 31 days to which no alterations were made.
- April (a lunar month) originally has 29 days. Caesar added a day to give it a total of 30 days.
- May also has 31 days and was remained unchained up to this day.
- The month of June originally had 29 days and Caesar gave it one extra day to make it 30.
- Caesar gave July (named after Julius Caesar) 31 days.
- August (as a lunar month), it originally has 29 days and Caesar added one day to it to make 30 days. As noted above, Emperor Augustus added one day to August (named after Emperor Augustus) which he removed from February.
- September has 29 days when it is in the lunar calendar. Caesar added two days to September, but Augustus reduced it to 30 days.
- October originally has 30 days in the Caesar calendar, but Augustus added one more days to make it 31.
- November originally has 31 days under the Caesar calendar, but again Augustus removed one day to it to make it 30.
- For December, it originally has 29 days and Caesar added one to make it 30. And Augustus added one more day making it 31 days.
Today, the most important thing that we learned from these alterations is that the calendar was more accurate to have 365 days.