Sikhs have traditionally recognised two eras and luni-solar calendars: the Nanakshahi and Khalsa. Traditionally, both these calendars closely followed the Bikrami calendar with the Nanakshahi year beginning on Katak Pooranmashi (full moon) in March and the Khalsa year commencing with Vaisakhi in April. The Nanakshahi Calendar is named after the founder of the Sikh religion, Guru Nanak Dev Ji. The Nanakshahi calendar is a tropical solar calendar used in Sikhism. It is based on the Twelve Months which is composed by the Sikh gurus reflecting the changes in nature conveyed in the twelve-month cycle of the year. The year begins with the month of Chet, with 1st Chet corresponding to 14 March every year. The reference era of the Nanakshahi calendar is the birth of Guru Nanak Dev, corresponding to the year 1469C.E. Banda Singh Bahadur adopted the Nanakshahi calendar in 1710 C.E. after his victory in Sirhind (12 May 1710 C.E.). According to which the year 1710 C.E. became Nanakshahi 241. The revised Nanakshahi calendar was designed by Pal Singh Purewal to replace the Bikrami calendar.Features of the original Nanakshahi calendar (2003 Version):

• Uses the accurate Tropical year (365 Days, 5 Hours, 48 Minutes, 45 Seconds) rather than the Sidereal year.

• Called Nanakshahi after Guru Nanak (Founder of Sikhism).

• Year 1 is the Year of Guru Nanak's Birth (1469 CE). As an example, March 14, 2023 CE is Nanakshahi 555.

• Is Based on Gurbani – Month Names are taken from Guru Granth Sahib.

• Contains 5 Months of 31 days followed by 7 Months of 30 days.

• Leap year every 4 Years in which the last month (Phagun) has an extra day.

• Approved by Akal Takht in 2003.