The Nanakshahi calendar, a fixed solar calendar intended to give Sikh gurpurabs and festivals stable annual Gregorian dates instead of the shifting dates a lunar reckoning produces, was formally adopted by the Shiromani Gurdwara Parbandhak Committee in 2003, designed by the Sikh scholar Pal Singh Purewal specifically to end the older reliance on the Hindu lunar Bikrami calendar that most Sikh festival dates had traditionally followed. The reform proved contested rather than settled: the Akal Takht, under pressure from traditionalist bodies including the Damdami Taksal and some diaspora organisations that objected to moving away from the older lunar dates their communities had always used, backed amendments in 2010 that restored lunar reckoning for a number of major gurpurabs, including this one, even while other events kept the fixed Nanakshahi dates.
The result is a calendar genuinely split down the middle, some Sikh observances fixed permanently to the same Gregorian date every year under the Nanakshahi reform and others, including Guru Gobind Singh's own birthday gurpurab, still calculated by the older lunar method depending on which authority and which gurdwara a given community follows, a live and only partially resolved institutional disagreement about Sikh timekeeping that continues to produce different published dates for the same festival from different Sikh organisations in the same year.