The Sikh tradition does not celebrate “holidays” the same way as other religious traditions. In Sikhi, no particular time or space is holier than any other — the divine is seen to permeate all time and space equally. At the same time, there are certain days of historical significance on which Sikhs around the world gather for reflection and celebration. The most common is the Gurpurab, which marks the anniversary of the birth or death of a Guru.
There are a few other days in a calendar year that continue to serve as times for gathering and celebration. The most prominent of these is Vaisakhi, the day on which the tenth Sikh guru, Guru Gobind Singh, created the Khalsa Panth, the community of initiated Sikhs. Another such day is Hola Mohalla, an occasion on which Sikhs have gathered together to celebrate martial arts and physical feats. Bandi Chor Divas, which typically comes in the fall, marks the day on which the sixth guru, Guru Hargobind, was released from wrongful imprisonment and returned to the community.
The dates for Sikh celebrations seem to vary because they are not based on the Gregorian calendar (the international civil calendar). Rather, Sikhs use their own calendar — the Nanakshahi calendar — which is a solar calendar that begins with the birth of Guru Nanak. The two calendars align for the most part, but a few slight variations make it difficult to pinpoint a single date on which these occasions and celebrations fall.