astronomy

Indian national calendar

Indian national calendar is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Indian national calendar rather than just read about it. In short: The Indian national calendar, also called the Shaka calendar or Śaka calendar, is a solar calendar that is used alongside the Gregorian calendar by The Gazette of India, in news broadcasts by All India Radio, and in calendars and official communications issued by the Government of India. It was adopted in 1957 following the recommendation of the Calendar Reform Committee. Śaka Samvat is generally 78 years behind the…

Key takeaways

Indian national calendar belongs to astronomy; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Indian national calendar to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Indian national calendar from memory before moving on to harder problems.

Reference excerpt

The Indian national calendar, also called the Shaka calendar or Śaka calendar, is a solar calendar that is used alongside the Gregorian calendar by The Gazette of India, in news broadcasts by All India Radio, and in calendars and official communications issued by the Government of India. It was adopted in 1957 following the recommendation of the Calendar Reform Committee. Śaka Samvat is generally 78 years behind the Gregorian calendar, except from January–March, when it is behind by 79 years.

Calendar structure The calendar months follow the signs of the tropical zodiac rather than the sidereal zodiac normally used with the Hindu and Buddhist calendars.

Chaitra is the first month of the calendar and begins on or near the March equinox. Chaitra has 30 days and starts on 22 March, except in leap years, when it has 31 days and starts on 21 March. All months other than Chaitra start on fixed dates in the Gregorian calendar. The months in the first half of the year all average out to having 31 days, to take into account the slower movement of the sun across the ecliptic at this time. This is similar to the Iranian Solar Hijri calendar. The names of the months are derived from the older Hindu lunisolar calendar, so variations in spellings exist, and there is a possible source of confusion as to what calendar a date belongs to. The traditional lunar calendar months were named based on the position of the Full Moon (opposite the Sun), thus the solar month names are derived from lunar nakshatra 180° from the position of the Sun. The names of the weekdays are derived from the seven classical planets (see Navagraha). The first day of the week is Ravivāra (Sunday). The official calendar reckoned by the government of India has Sunday as the first and Saturday as the last day of the week.

Years are counted in the Shaka era, which starts its year 0 in the year 78 CE of the Common Era. To determine leap years, add 78 to the Shaka year – if the result is a leap year in the Gregorian calendar, then the Shaka year is a leap year as well.

History Senior Indian Astrophysicist Meghnad Saha was the head of the Calendar Reform Committee under the aegis of the Council of Scientific and Industrial Research. It was Saha's effort which led to the formation of the committee in 1952. The task before the committee was to prepare an accurate calendar based on scientific study, which could be adopted uniformly throughout India. The committee had to undertake a detailed study of thirty different calendars prevalent in different parts of the country. The task was further complicated by the integration of those calendars with religion and local sentiments. In 1954 the committee recommended a fixed tropical solar calendar for use as a unified national civil calendar, which was adopted as the Indian national calendar. A tropical lunisolar calendar was also proposed for religious purposes but this recommendation was not accepted. India's first prime minister, Jawaharlal Nehru, in his preface to the Report of the committee, published in 1955, wrote:

"They (different calendars) represent past political divisions in the country ... . Now that we have attained Independence, it is obviously desirable that there should be a certain uniformity in the calendar for our civic, social, and other purposes, and this should be done on a scientific approach to this problem." Usage started officially on 1 Chaitra 1879 Saka Era, or 22 March 1957. However, despite the government's attempts to propagate the calendar through official Rashtriya Panchangs, the Indian national calendar did not find acceptance with panchang makers or the general public, and current usage is largely limited to governmental offices. Existing calendars based on the Saka era remain in use, which can lead to confusion.

Illustrations

Worked examples

Example 1 — a first encounter with Indian national calendar

Start with the simplest possible case. Write down what Indian national calendar claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Indian national calendar before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Indian national calendar ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Indian national calendar

In research: Indian national calendar appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Indian national calendar in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Indian national calendar is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1957 introductions, Culture of India, Months of the Hindu calendar, so understanding it makes those chapters shorter.
In everyday life: Look for Indian national calendar outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Indian national calendar in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Indian national calendar means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Indian national calendar out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Indian national calendar in simple terms?

Why does Indian national calendar matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Indian national calendar?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Indian national calendar.