Calendar History - Romulus to Gregorian

Today's Gregorian Calendar is a refined version of the earlier Roman Calendar. Following is the effort to understand what the Roman Calendar & the time chronology was and how it kept on changing. However before proceeding further, few things have to be understood:

1. One year is the time the Earth takes to rotate the Sun

2. What is the exact period of one year? As per the scientific calculation, one year equals to -

365 days

5 Hours = 0.20833 days

48 minutes = 0.03333 days

46 seconds = 0.0005324 days


One year = 365.242192 or 365.2422 days

3. Adjusting to this seasonal cycle can be termed as updation of calendar over the period of time

4. Since the period of the year is in decimal days, it becomes extremely difficult to adjust the calendar to match the Earth's one year. It is practically not feasible to calculate few hours this year, few hours next year. All human transactions are based on the day as a unit. But it is possible to match our calendar year to the Earth's year in different methods. Hence there were many calendars as well as time calculation methods.

Once we understand above concept, it would become easier to know how the calendar updation took place.

753 BC

The emperor, Romulus was the founder of the Rome city as well as the Roman Empire. He had devised a method to calculate period which was known as Romulus Calendar. How was this calendar? There were 304 days of the year in this calendar and there was absolutely no scientific base for such number. There were 10 months in the year. The names of the months & number of days were as under:-

1st Month - Martius (March) = 31

2nd Month - Aprilis (April) = 30

3rd Month - Maius (May) = 31

4th Month - Junius (June) = 30

5th Month - Quintilis (July) = 31

6th Month - Sextilis (August) = 30

7th Month - September = 30

8th Month - October = 31

9th Month - November = 30

10th Month - December = 30

Total Number of Days = 304

There used to be no calculation for days after December as all transactions used to come to standstill on account of severe winter. Arrival of Spring was considered as beginning of the year and calculation started from the month of March. There is no other more unscientific calendar than this but funnily enough names 8 months of the current calendar are taken from this calendar. It would be also be fun to know how these names came into existence.

Martius - means Mars who was Roman God of War. Since Roman were known for their war victories, the name is the first month was kept as Martius - Mars - March. In the month of March (21st March), the Sun crosses the Equator and enters the Northern Hemisphere and hence metaphorically the concept was that the Sun has marched to defeat the winter.

Aprilis - Venus is the Greek Goddess of love & beauty and she was also known as Aphrodite. The Roman slang for Aphrodite was Aprilis or April. With the advent of spring, the whole of Europe used to be beautiful and may be this name was given for the month.

Maius - Maius (May). The name of the daughter of Roman God, Atlas, was Maia and this name was given for the month.

Junius - Greek Super God (महादेव) was considered to be Jupiter and name for this month was derived from his wife's name, Juno to Junius to June.

Quintilis to December simply means Fifth to Tenth. Since no special names were given for further months, we can also jokingly say that they had no more God's or Goddess's. But since this Romulus calendar was completely unscientific, it was imperative that the same should be improved.

715 BC

This year Numa Pompilius succeeded Romulus as the Roman Emperor. He appointed committee of counselors named Pontifices to prepare calendar every year. The chairman of this committee was titled as Pontiphex Maximus. The Pope in Rome still carries that title today. The committee made following changes:-

Two months viz. February & January, in this order, of 28 days each were added after December hence they increased 56 days in the year. But Romans never liked even numbers and one day was reduced from the months of 30 days of the Romulus calendar and one day was added to January to make it 29 days. Hence the days in the year were as under:-

Martius, Aprilis, Maius, Junius

(4 months X 31 days = 124 days)

Quintilis, Sextilis, September

October, November, December

(6 months X 29 days = 174 days)

February 28 days

January 29 days

Total Number of Days = 355

The Lunar Year is of 354 days and this year had one day extra. In order to match the seasonal cycle, Numa Pompilius made provision of adding extra month known as Arsidonius.. However the authority to decide when & how to take this additional month was given Pontifex Maximus. The calendar of Numa Pompilius was in existence till 450 BC.

450 BC

This year the committee of counselors amended the Roman Calendar and decided how to take additional months. They also decided to change the order of months and hence January followed December and February became the last month of the year. It was decided to take additional month of 22 and 23 days in the even year. Hence:-

1st Year (Odd Figure) = 355 days

2nd Year (Even Figure) = 377 days

3rd Year (Odd Figure) = 355 days

4th Year (Even Figure) = 378 days

Total Number of Days = 1465 Days
Hence average days per year
= 1465 / 4 = 366.25

But that meant that the days in the calendar were more by 1 day of actual year of 365.2422 days. This one day difference created enormous problems for the Pontifices committee.

Julian Calendar

This calendar came into existence in 45 BC. Julius Caesar was appointed as the Pontifex Maximus in the year 63 BC and hence became the chairman of committee which took decisions about the calendar. However he completely neglected the issue of calendar on account of internal dissension in the Roman Empire. Around the year 48 BC, Caesar went to Egypt and fell in love with Cleopatra and he stayed in Alexandria for a year or so. During his stay, he studied the Egyptian method of time & season calculation. Egyptian Scientists had realised the year is of 365.25 days and hence they had a year of 365 days consisting of 12 months of 30 days each ending with 5 days of festivities. Their week was for 10 days. The emperor of Egypt, Ptolemi was first to propose in 240 BC, that the difference of 0.25 days be adjusted by taking 6 days of festivities instead of 5 days, every 4 years. However the religious leaders did not support him and his proposal was rejected. But today we must acknowledge that Ptolemi was truly the conceptualizer of the Leap Year.

Caesar invited Egyptian Mathematician, Sosigenes, to update the calendar. As per Sosigenes's suggestion, the Roman Calendar became for 365 days and every fourth year of 366 days to adjust with the Earth's year of 365.25 days. However in order to match with the Spring Equinox Day, the number of days for the year 46 BC were raised to 445 days and there was complete chaos and hence 46 BC is known as the Year of Confusion. Following is the chart for the years 47 BC, 46 BC & 45 BC.

Month (47BC), (46BC), (45 BC)

Jan - 29, 29, 31

Feb - 28, 28, 29 or 30

Extra -- 27 --

March - 31, 31, 31

Apr - 29, 29, 30

May - 31, 31, 31

Jun - 29, 29, 30

Jul - 31, 31, 31

Aug - 29, 29, 30

Sep - 29, 29, 31

Oct - 31, 31, 31

Nov - 29, 29, 31

Addl -- 34 --

H Dec -- 34 --

Dec - 29, 29, 30

–––– –––– ––––

Total Days

355, 445, 365

This is how Julian Calendar came into effect in 45 BC which was for 365 days and every 4th year of 366 days terming it as Leap Year.

Amendments by Emperor Augustus in the Julian Calendar:-

The Julian Calendar came into effect in 45 BC but within a year, in 44 BC, Julius Caesar was murdered and hence the responsibility of implementing the calendar rested on the shoulders of Pontifices Committee. Though it was decided to take leap year of 366 days every 4 years, the committee either inadvertently or purposely started taking leap year every 3 years. On account of this blunder, the correctness of Julian Calendar was lost but this continued from 45 BC till 8 BC.

Gaius Octavius (Augustus), grandson of Caeser's sister and adopted son of Julias Caeser, took over the reins of Roman Empire when he was only 19 years old. He appointed himself as Pontiphex Maximus in 27 BC and became the chairman of the calendar implementation committee. He realised the mistake of leap year.

In the 36 years, from 45 BC till 9 BC, 13 leap years were taken instead of 10 and hence 3 extra days were taken. In order to adjust that anamoly, it was banned to take leap year from 4 BC to 4 AD and the Julian Calendar was brought on track again. The system of taking leap year every 4 years is being followed from 8 AD till today.

The Roman Senate passed a resolution to felicitate Augustus and changed the name of the month after July from Sextilis to August. Earlier the month of Quintilis was also renamed as July, as honour to Julius Caeser. As per the Julian Calendar, the number of days in the Sextilis (August) were 30 whereas July had 31 days and this was not acceptable to Augustus. Hence he reduced 1 day from February and added in August to make it 31 days. This change made July, August & September as 3 consecutive months of 31 days. The Julian Calendar had a order of alternative months of 31 and 30 days and hence one day from September was given to October and one day from November was given to December in maintain the order.

Following is list of months & number of days as per Julian and Augustus Calendar:-

Month, Julian, Augustus

January - 31, 31

February - 29/30, 28/29

March - 31, 31

April - 30, 30

May - 31, 31

June - 30, 30

July - 31, 31

August - 30, 31

September - 31, 30

October - 30, 31

November - 31, 30

December - 30, 31

––––––––– –––––––––

Total Days:

365/366, 365/366

Today we are following the days as per Augustus Calendar and the names of the months were also agreed upon. Though this amendments were made by Augustus, the calendar's name remained as Julian Calendar.

Julian Calendar was the predominant calendar in the Roman world, most of Europe, and in European settlements in the Americas and elsewhere.

It must also be noted that year after 1 BC was no year zero but the calendar goes straight from 1 BC to 1 CE, complicating the process of calculating years..

Shortcomings of the Julian Calendar
As per this calendar, every year is of 365.25 days. However the time taken by Earth to rotate around Sun, by scientific calculation, is 365.2422 days. This is known as Equinox Year. Hence it can be noticed that the Julian Calendar year is greater than 0.0078 days than Equinox Year. Although Greek astronomers had known, at least since Hipparchus, a century before the Julian reform, that the tropical year was slightly shorter than 365.25 days, the Julian calendar did not compensate for this difference. And this will amount to 1 day difference every 128 years. If we consider thousands of years, the seasonal cycle (which is based on Equinox Year) and the calendar will have lot of difference.

Beginning of Gregorian Calendar
Gregory XIII became Pope in 1572 CE. However till that time the scientists had realised that due to Earth Axis Oscillation the Summer Equinox is shifting behind. However as per the Religion Council's decision in 325 CE, it was mandatory to keep 21st March as the Summer Equinox Day. Ever the Easter Festival was dependent on this day. Hence Pope appointed a committee of Astronomers under the leadership of Christopher Clavius to suggest improvements in calendar. Following is the Chart to show how the summer equinox was shifting behind..

Year - Summer Equinox
325 - 21st March
453 - 20th March (128 years)
581 - 19th March
709 - 18th March
837 - 17th March
965 - 16th March
1093 - 15th March
1221 - 14th March
1349 - 13th March
1477 - 12th March
1605 - 11th March

This discrepancy was corrected by the Gregorian Reform of 1582. And accordingly the Julian Calendar was refined and gradually replaced by the Gregorian Calendar, promulgated in 1582 by Pope Gregory XIII. The Gregorian calendar has the same months and month lengths as the Julian calendar, but, in the Gregorian calendar, years evenly divisible by 100 are not leap years, except that years evenly divisible by 400 remain leap years.

The following photo shows that 11 days were added in the Julian Calendar in October 1582.

Consequently the Julian calendar is currently 13 days behind the Gregorian calendar.

It is believed and accepted by all that Jesus Christ was born on 25th December. Actually there is no scientific evidence to prove that. In fact most scholars believe that Jesus was born between 6 to 4 BC and that he died between 30 to 36 CE. During those days, 25th December used to be considered as birthday of the Sun and since Jesus was proclaimed as God in the Religious Council's meeting in 325 CE, it was said that he was born on that day.

There is funny anecdote to the Gregorian Calendar. Since it was promulgated by a Pope of a Catholic church, the Protestant Christians refused to accept the same. The British finally accepted this calendar after nearly 150 years. If this fact is taken into consideration, the birthday Chhatrapati Shivaji Maharaj may not be 19th February as it was as per Julian Calendar but actually may be 29th February or 1st March or so if Gregorian Calendar was considered. (Anybody interested in creating one more controversy about Shivaji's Birth Date?)

Shortcomings of the Gregorian Calendar
1. Currently there is a difference of 0.0003 days (26 seconds) between Gregorian Year and Equinox Year. This will create 1 day difference after 3333 years and Summer Equinox will fall on 20th March. Currently this difference is negligible.
2. The starting of year on 1st January has no scientific base. As per Hindu time calculation, year starts around Summer Equinox. This calendar is Lunar based and hence Gudhi Padwa doesn't exactly fall on 21st March but definitely is around that time.
3. There is no meaning to the name of the months in Gregorian Calendar. These names are either based on some Gods or Personalities or numbers. However as per Hindu Calendar, based on the moon position in a particular constellation on the full moon day, the name of that constellation is given to that month. e.g. On the full moon day of Chaitra, the moon is in Chitra Constellation.

We may now realise the kind of efforts have gone in to make a near perfect calendar from 753 BC to 1582 AD; that’s nearly 2335 years!!!! However we must remember that Equinox Year is in decimal days and 100% accuracy will never be achieved.

(I am sorry that the charts have not been presented properly but that seems the issue in WordPress)

Yeshwant Marathe

Sudhir Dandekar

#GregorianCalendar #history #calendar #julian

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