Hindus, Christians, Muslims, Sikh, Jain, Buddhist, and others have celebrated throughout the world and wished everyone in social media, voice calls and in person, “Happy New Year”. My curiosity sparked when I heard a speaker in the news channel greeting in a different manner which made me to think about the history of Gregorian Calendar and then my research started to explore as well as to understand the science behind calendar making. The information provided in this article is based on the data provided by historians, learned scholars, theologians from the Vatican Church, Hindu literatures, and researchers working in the fields of Indian Knowledge System.
Julian Calendar
During the Roman Civilization which is an advancement of the Greek civilization, people were following a solar calendar but it had only 304 days in a year and the new year begins in the month of March and ends with December. They were having trade with various countries and approximately 30 to 35% of their revenue was coming from Indian market. As females and males were fond of Indian textiles, Damascus steel, spices, etc., and the pressure from merchants made them to have an account of yearly basis contracts on getting the goods, the Roman empire decided to take 51 days from the Lunar calendar (Chandramanasa) which is followed by Indians and made their calendar to 355 days.
The Romans had a practice of naming their months based on their Gods, festival practices, and the number system. For example, the first month of the year, March is based on the Roman God of War – Mars, second month April is based on the number for second month of Rome which is called Aphrilis, September is from Septem which is seven or Sapthah (in Sanskrit), October is from Octo which is eight or Ashtah, November is from Novem which is nine or Navah, December is from Decem which is ten or Dashah. The months which were added based on the Lunar calendar of Indian system are January which is based on the name of Roman God Janus and the month February is based on the purification festival – Februa. These two months, i.e., January (30 days) and February (25 days) were declared as holidays for celebrating their achievements and growth (as they were aware that in their calendar errors have to be corrected).
In AUC (Ab Urbe Condita) 708, (i.e., 45 BCE), in the regime of the emperor Julius Caezar, he corrected few errors which was previously mentioned in the Roman calendar and with the help of the Alexandrian astronomer, Sosigenes reformed the calendar, making the number of days to 365.242 days as per the solar calendar (Sauryamanasa) used in Indian Solar calendar and in other civilization thereby creating the Julian Calendar in AUC 709 (44 BCE). After the assassination of Julius Caezar, the Roman Senate renamed the fifth month of Roman calendar – Quintilis on his name as “Julius” in his honor which later changed to “July” and took one day from February and made Julius as 31 days. After the regime of Julius Caezar, the emperor Augustus came to the power (ruled from 27 BCE to 14 BCE) and he said “Am I a Caezar any less?” thereby the Roman Senate renamed the sixth month which was called Sextilis to “August” and like Julius month, here also one day was taken from February, added to August making it as 31 days.
In Julian Calendar, since it has 365.242 days, to make up the 0.242 days they have rounded off the value to 0.250 days. For making of 0.250 days to one day, they have evolved with an idea of implementing the rule in the calendar that every 4th year would be leap year and one day would be added in February to makeup the values. From that period onwards we are having 29 days in February for every leap year.
Gregorian Calendar
With increasing corruption, administrative problems, barbaric attacks from Germanic tribes, the downfall of the Roman Civilization slowly started and for filling up the vacuumed space in the Roman Senate, the consortia of churches and monastery played a vital role which was set on the principles of Christianity to establish the Roman Catholic and became the base for the rise of Vatican Church and monastery. In AUC 1089 (336 CE), a group of the monk senate from the Vatican Church, for glorifying the birth of the Lord Jesus Christ decided to celebrate his birth day. But they were not sure about the date in the history and based on the clues available in various Bible references, took 25th December which is a winter solstice day (having a long day with more sunlight) and started celebrating the whole December month with joy and happiness to spread the message of the Lord. Based on the winter solstice, those eastern countries where the Julian calendar is still in practice, people celebrate Christmas on 7th January only based on the astronomical reference of 15th Century CE and not on 25th December.
In 1582 CE, Pope Gregory XIII, reformed the Roman Julian Calendar by correcting various mistakes and deleting several days from the calendar making it as the official calendar for use. This calendar is called as Gregorian Calendar which declared the January 1st as New year to the mark in the history that we are living in a Samvat or Era where the birth of the Lord Jesus Christ happened. Also taking in to the accounts made in the past by various monks, systematically they changed the concept of Roman year from AUC to Before Christ (BC) and Anno Domini (AD) which means “In the year of the Lord”. The timeline selected for the start of AD is still in ambiguity because as per researchers, there is no year called zero so that BC ends and AD starts.
In the 17th Century when French Revolution happened, many questioned about the addition of religion in the calendar in the form of BC and AD, due to which it has been changed in a subtle way as Before Common Era (BCE) and Common Era (CE) where Common Era is also reflecting towards the “The Year of the Lord”. With the rise of the British Empire dominating various countries around the world, the practice and usage of Gregorian Calendar came into effect and still practiced except in few eastern countries where Julian Calendar is still in practice.
Indian Hindu Luni-Solar Calendar
The history of Indian Hindu Luni-Solar Calendar dates back to approximately 38000 years back based on the Surya Siddhanta where the Rishis have explained each method of calculating the position of Nakshatras (27 Stars) based on the position near the Moon, the distance covered by the Moon from the Sun, transition of waxing phase means the Moon is growing leading to full Moon (Purnima) which is called the Shukla paksha and waning phase means the Moon is shrinking leading to dark phase (Amavasya) which is called Krishna paksha, positioning of planets at the dawn, complete rotation of Sun in its axis, etc. But the number of days in a year as per the Surya Siddhanta calculation was 360.242 days per year.
Later in the period of the King Vikramaditya, taking the mathematical calculation based on the theories of Acharya Aryabhata and his Arya Siddhanta, a new calendar was reformed with 365.242 days per year. This is called as Vikram Samvatsara. Also to understand the movement of the earth revolution around the Sun in the axis, the Hindu Luni – Solar Calendar consist of 60 cyclic period which is named differently for each year starting from Prabhava (Manifestation) and ends with Akshaya (Imperishable). Presently from March 2025 to March 2026, we are in the Viswavasu Samvatsara which is the 39th cyclic period. The starting of a new year is celebrated and called as Ugadi, Yugadi, Gudipadwa, Vishu, Puthandu, Bohag Bihu, Pohela Boishakh, Cheti Chand, Navreh, Vaisakhi, Chaitti, etc., in different parts of our country.
These are some of the factors which determine the fundamentals of forming the scientific Hindu Luni – Solar Calendar based on the Astronomical data which is called as Panchangam having Tithi (based on the angular distance between the Moon and Sun which is 12o), Vara (the Deity preceding that day), Nakshatra (the position of star near moon), Yoga (calculated from the sum of the longitudes of the Sun and the Moon) and Karnam (a time segment used to determine activities and muhurta and half of the Tithi, i.e., 6o). The advantage of using the Hindu Luni – Solar Calendar when compared to other calendar is to mathematically calculate based on the astronomical changes and to predict the climate, season, eclipse, time, day, etc.
In the Lunar calendar, the month calculation depends on from one Purnima to another Purnima where the moon completes one rotation of waxing and waning comprising of approximately 29.53 days which is made as 30 days. In Solar calendar, the month calculation depends on from one Amavasya to another Amavasya and also the Sun moves from one Rasi (Solar signs) to another Rasi comprising of 30 days. For example, every year the Sun covers the distance from the Dhanur Rasi (Sagittarius) to the Makara Rasi (Capricorn) on either 14th or 15th January as per Gregorian Calendar and has the longest day of the winter solstice. Therefore, the period after 14th or 15th January is considered as the “Uttarayana punya kalam”, i.e., considered as the most auspicious period.
Since the Gregorian calendar which was reformed from the Julian calendar also follows the same Hindu Solar Calendar, therefore the Makra Sankranthi falls on the same dates but the Tithi for the Sankramanam, i.e., crossing point changes making it to fall on either 14th or 15th of January every year. But another point as per Arya Siddhantha and Surya Siddhantha we have to consider is the revolving path of the Earth in the axis and precession, due to which the fall of equinoxes changes in the course of time and the Rishis have considered to add one day for every 70 – 72 years. Due to this concept, the winter solstice which had fallen on 25th December in the 4th Century CE (reason for considering the date as the birth of Lord Jesus Christ) is now falling on 14th or 15th January in the 21st Century CE as per Hindu Arya and Surya Siddhantha.
Another important aspect of Luni Solar calendar is the naming of each month. In Lunar Calendar (Chandramanasa), the naming of the month depends on the position of the Nakshtra (Star) present near the full moon day (Purnima) and the angular distance covered by the moon from the sun that is why in the parts of Northern India the names of the month changes when compared to the Southern India where we follow the Luni – Solar calendar. For example, the Nakshtra near the full moon day at the beginning of the month as per the Amanta system in the Lunar calendar which is followed in the South India (mid of November to mid of December and ends on Amavasya) is Margasirsa Nakshtra and as per the Purnimanta system in the Lunar calendar which is followed in the North India (mid of December to mid of January and ends on Purnima) is Pausa month with the Sravana Nakshtra near the full moon.
In the Lunar calendar, another important aspect is the presence of approximately 355 days and in the Solar calendar, it is 365.242 days. For making up the gap in the calendar, every third year approximately 33 days are added in the Lunar calendar and these approximately 33 days are called as “Adhika masam or Extra month” to cover the count of 365.242 days per year which is present in the Solar calendar and depending on the climate, season and environment, the Adhika masam is calculated and added along with a selected month in every third year.
The Panchangam reminds us that time is not just counted—it is lived. By reconnecting with lunar and solar cycles, we rediscover an ancient yet timeless wisdom from our Luni – Solar Calendar system but we also follow the Gregorian calendar since it has been practiced everywhere in the world.