Guru Gobind Singh, the tenth Sikh Guru, installed the Siri Guru Granth Sahib as Guru October 20, 1706. This day is celebrated today as “Guru Gaddi Day” each year. This is often celebrated with special Kirtan programs, Akhand Paths (continuous reading of the full Siri Guru Granth Sahib) and Sikh parades.
At the time of His death in 1708, Guru Gobind Singh Ji passed the mantle of the Guruship to the Siri Guru Granth Sahib. This ended the time of the physical Gurus of the Sikhs. Guru Gobind Singh Ji declared that the Word of God, embodied in the Siri Guru Granth Sahib, was to be Guru for the Sikhs for all time. He said:
“O Beloved Khalsa, let any who desire to behold me, behold the Guru Granth. Obey the Granth Sahib, for it is the visible body of the Guru. Let any who desire to meet me, diligently search its Bani.”
The Siri Guru Granth Sahib remains the Spiritual Light and Guide for the Sikh community today.
Sourced from https://www.sikhdharma.org/topics/guru-gaddi-day-2