In Sikhism , it remembers the creation of the Khalsa at Anandpur Sahib in 1699 , by the 10th Sikh Guru , Guru Gobind Singh . In Sikhism , it is one of the most significant holidays in the Sikh calendar , commemorating the establishment of the Khalsa at Anandpur Sahib in 1699 , by the 10th Sikh Guru , Guru Gobind Singh .