The Sun is the main source of energy for all life on Earth. We know now that Vitamin D, which the human body makes only when exposed to the Sun, is very important for our wellbeing.

The importance of the Sun was recognized in the Puranas. The ancient Indian calendar divided the year into two halves – Uttarayana and Dakhinayana.

Since India is in the Southern Hemisphere, Uttarayana (Uttar means north) was defined as the six months of the year when the Sun travels from Capricorn to Cancer. It begins with the winter solstice, when the day is at it shortest and the night, longest. During this six month period, the days become longer and as a result we are exposed to more sunlight, and in turn the body synthesizes more Vitamin D. Perhaps for this reason, the Puranas considered Uttarayana as an auspicious time.

Dakshinayana (Dakshin means south) was defined as the six months of the year when the Sun travels from Cancer to Capricorn. It begins with the summer solstice, when the day is at its longest and the night, shortest. During this six-month period, the days become shorter and as a result we are exposed to less sunlight, and therefore the body’s intake of Vitamin D may not be optimum. This in turn, may affect a person’s mental and physical well-being. Perhaps for this reason, Indian traditions encourage fasting and meditation during these six months.

The civil calendar is the calendar used within a country for civil, official or administrative purposes. The most common civil calendar and de facto international standard is the Gregorian calendar, which is associated with the Catholic Church and the papacy. It has been adopted, as a matter of convenience, by many secular and non-Christian countries.

The Indian national calendar, sometimes called the Saka calendar or the Panchanga, was introduced in 1957 based on the traditional Hindu calendars. Senior Indian Astrophysicist Meghnad Saha was the head of the Calendar Reform Committee. The committee received support from the Council of Scientific and Industrial Research and their task was to prepare an accurate calendar based on scientific study, which could be adopted uniformly throughout India. It was a huge task. The Committee had to undertake a detailed study of different calendars prevalent in different parts of India. There were thirty different calendars!

The Indian national calendar is the official civil calendar in use in India. It is used, alongside the Gregorian calendar in communications issued by the Government of India. The Hindu calendar is also important to the practice of Hindu astrology and zodiac system, most of which it adopted from Greece, in centuries after the arrival of Alexander the Great.


A Tithi or lunar day is calculated when the moon moves 12 degrees eastwards from the sun.

The Length of a Tithi

Tithis begin at varying times of day and vary in duration from approximately 19 to approximately 26 hours.

Since the motions of the sun and the moon are always varying in speed, the length of a Tithi constantly alters. Sometimes a tithi can be as long as 26 hours and as less as 21 hours 34 minutes and 24 seconds. This means the time a tithi begins varies with the general time followed in a country.

Same Tithi on two days and Two Tithis on one day

Sometimes a tithi might begin and end on the same day. Thus there will be two tithis on day. For example – you might see a Tritiya and Chaturthi on the same day Sometimes a tithi might overlap into the next day and then there will be two same tithis ontwo consecutive days. For example – it will be Tritiya on Sunday and Monday.

Days / Vasaras

Why are the days named after planets?

In Ancient Greek and Roman civilization, the classical planets referred to the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn, which could be seen with the naked eye in the sky. Now, since most of the Hindu calendar was adopted from Greece, in centuries after the arrival of Alexander the Great, the days of the week have been named after the sun, the moon and the five known planets. These planets were themselves named after deities of their respective cultures. So, in effect the names of the days originated from the names of Gods and Goddesses in local cultures.