Sikhs celebrate Hola Mahalla or simply Hola in place of Hindu festival of Holi. It takes place on the first of the lunar month of Chet, which usually falls in March. This falls generally next day to Holi; Hola is the masculine form of the feminine noun Holi.
According to Wikipedia, Mahalia, derived from the Arabic root hal (alighting, descending), is a Punjabi word that implies an organized procession in the form of an army column accompanied by war drums and standard-bearers, and proceeding to a given location or moving in state from one Gurdwara (Sikh temple) to another.
This custom was started by Guru Gobind Singh (1666-1708) who held the first march at Anandpur Sahib, the place where Khalsa, the militant version of the Sikhs was also created by the same Guru. The first Hola was held on Chet vadi 1, 1757 Bk (22nd February, 1701).
Unlike Holi, when people playfully sprinkle colored powders, dry or mixed in water, on each other the Guru made Hola Mahalla an occasion for the Sikhs to demonstrate their martial skills in simulated battles. This was probably done forestalling a grimmer struggle against the imperial power following the battle of Ninnohgarh in 1700. Holla Mahalla became an annual event held in an open ground near Holgarh, a Fort across the rivulet Charan Ganga, northwest of Anandpur sahib.
The popularity of this festival may be judged from the fact that out of five Sikh public holidays requested by the Khalsa Diwan, the then Chief seat of Sikhs of Lahore in 1889, the then British Government approved only two - Holla Mahalla and the birth anniversary of Guru Nanak.
Hola Mahalla is presently the biggest festival at Anandpur Sahib in addition to Baisakhi. The town of Anandpur Sahib is located near Rupnagar (Ropar) in Punjab at the foot of Shivalik hills.
For the current year 2015, it will be celebrated on 6th March. (With inputs from Sikh Wiki)