The national calendar of India, based on the Saka era, was officially adopted for use along with the Gregorian calendar from:

The national calendar of India, based on the Saka era, was officially adopted by the Government of India from 22 March 1957, which corresponded to 1 Chaitra 1879 of the Saka era.

Background:

At the time of Independence, about thirty different calendars were in use in different parts of India.

In 1952, the government set up the Calendar Reform Committee, headed by the astrophysicist Dr. Meghnad Saha, to prepare a unified and scientific calendar.

The committee recommended a reformed Saka calendar, which was accepted.

Features of the national calendar:

• It is based on the Saka era, which began in 78 CE (traditionally linked with the accession of the Kushana king Kanishka).
• It is a solar calendar, with 365 days in a normal year and 366 days in a leap year.
• It has 12 months: Chaitra, Vaisakha, Jyaistha, Asadha, Sravana, Bhadra, Asvina, Kartika, Agrahayana, Pausa, Magha and Phalguna.
• Chaitra is the first month; it begins on 22 March in a normal year and on 21 March in a leap year.
• The first months of the year have 31 days, and the later months have 30 days.

Use of the national calendar:

It is used, along with the Gregorian calendar, in the Gazette of India, in news broadcasts by All India Radio, and in calendars and communications issued by the Government of India.

How to find the Saka year:

The Saka year is about 78 years behind the Gregorian (Common Era) year.

About Meghnad Saha:

• He was a famous Indian astrophysicist, known for the Saha ionisation equation.
• He founded the Saha Institute of Nuclear Physics in Calcutta.

Why not the other options?

• ✗26 January 1950, 15 August 1947 and 1 April 1951 are not the date from which the national calendar was adopted.