To appreciate the new calendar given by Sardar Pal Singh Purewal, we take a brief look at other calendars in vogue.

Julian Calendar was among the earliest Christian Era (CE) calendars and was introduced in 46 BC by the Roman Emperor Julius Caesar (100 – 44 BC). It was based on the observation that the Earth completes its one revolution around the Sun in about 365.25 days, the period being unevenly divided into 12 months. This calendar was used during the lifetime of Jesus Christ and also for almost 1600 years thereafter. It is still in use in some Eastern Orthodox churches.

Pope Gregory XIII (1502-1585 CE) improved upon the Julian Calendar (both based on the Solar System) in 1582 CE by taking the period of rotation of the Earth around the Sun as about 365.2425 days. This is also known as the Gregorian calendar and is used nowadays almost all over the world.

Bikrami Era (BE) calendar, based mainly on the Lunar System, is being followed by many in India. Earlier, the Sikhs also followed it. In it, the duration of each month is approximately 29.5 days. This is the average time the Moon takes to complete one full rotation around the Earth. The Bikrami calendar year, therefore, is of 354 days. Bikrami is actually a merger of the Lunar and Solar cycles, in which the dates of the Gurpurabs and other festivals keep on changing every year. They are either behind by 10 or 11 days as compared to the Christian Era calendar or ahead by up to 18 or 19 days.

Mal Mas, or an extra (13^th) month is added to the Bikrami year to overcome this problem. This additional month was added after every 3 or 4 years arbitrarily. In this month, traditionally no Gurpurb or festival is celebrated as it is considered “inauspicious”. This view is not in accordance with Gurbani,  which says that: No month is bad, as all the months are related to Seasons. (“Barah Maha” in ) Sri Guru Gtanth Sahib, [14] [1] [136]. 

The idea of a Solar System-based calendar was given by Sardar Karam Singh, a famous historian (1884-1930), and was supported by scholars like  Professor Sahib Singh (1892-1977) and Bhai Randhir Singh (1878-1961), who felt that dependence on Aamavas and Puranmashi (basis of the Lunar calendar), is not supported by Gurmat (The Teachings of Guru Sahibs).

Nanakshahi Calendar was created by Sardar Pal Singh Purewal, who was born in the Jalandhar district of Punjab (in India) and was living in Edmonton (Canada) since 1974. This calendar follows the descriptions in the Sacred Sikh Scriptures and gets rid of the Bikrami (Luni-solar) calendar. It is a much improved Solar System-based calendar and is not in contradiction with the Gregorian calendar. On the 300th year of Khalsa Panth, the highest seat of the Sikh Spiritual and Temporal Authority, Sri Akal Takhat Sahib approved this new calendar, and the Shiromani Gurdwara Prabandhak Committee ( SGPC) released it. It was decided to celebrate the Gurpurabs according to this independent Sikh calendar.

Chet is the first month, and all months are according to the seasons, as mentioned in Gurbani. The first five months of the Nanakshahi year (Chet, Vaisakh, Jeth, Haarh, and Saavan) have 31 days each. The other seven months (Bhaddon, Assu, Kattak, Maghar, Poh, Maagh, and  Phaggan) have 30 days each. In a Leap year, the last month (Phaggan) has one extra day added to it. The dates of Gurpurabs and other festivals in it do not change every year. No ‘impure’ or ‘inauspicious’ (Mal Mas) month exists in the Nanakshahi calendar.

Nanakshahi calendar months correspond to the Gregorian ( or Christian) Era as follows.   

1 Chet: 14 March, 1 Vaisakh: 14 April, 1 Jeth: 15 May,  1 Haarh: 15 June, 1 Saavan: 16 July, Next, 1 Bhaddon: 16 August,  1 Assu: 15 September, 1 Kattak: 15 October,   1 Maghar: 14 November,  1 Poh: 14 December, 1 Maagh: 13 January, and 1 Phaggan: 12 February. Unlike the Bikrami Calendar, these (corresponding) dates do not change every year.  

Solar year (with about 365.2425 days) is the basis of both Nanakshahi and Christian Era calendars. However, the latter has an un-systematic distribution of days in the 12 months. There are 30 days in four months (September, April, June, and November) that are in no sequence. Seven others (January, March, May, July, August, October, and December) have 31 days, again in no particular order. The Leap month, February also does not form part of any sequence. In the Nanakshahi calendar, there is a sequential system of the first five months in a row, with 31 days each,  and the next seven months in a row, with 30 days each,  all in proper order. The Nanakshahi calendar starts from the date of Guru Nanak Sahib’s birth in 1469.

Sardar Pal Singh Purewal published a book that spans 500 years from 1469 onwards,  correctly giving the actual dates for numerous historical events as per his new calendar. It was published in 1994 by the Punjab School Education Board, Sahibzada Ajit Singh Nagar (Mohali). This almanac also provides comparative dates in the Lunar and Solar calendars,  and the Islamic or Hijri calendar (which he created). Many Gurdwara Committees, including Pakistan Sikh Gurdwara Prabandhak Committee, follow this original version of the Nanakshahi calendar.

In 2007,  the Government of Pakistan released the Hijri calendar prepared by Pal Singh Purewal, which helps to know the exact date and time of various Muslim festivals. For this, he was given the “Lifetime Achievement” award, and Dyal Singh College, Pakistan, dedicated its Library to his name. He was given Honorary Doctorate by the World Sikh University (U.K.) and the Queen’s Golden Jubilee Medal for his three-decade-long voluntary work. His contribution was also appreciated by the Alberta Legislature, in Canada. He expired on September 22, 2022, in Edmonton.