Wikipedia
Vaisakh (, ) is the second month in the Nanakshahi calendar. This month coincides with April and May in the Gregorian calendar and to Vaisakha in the Hindu calendar; it comprises the time of crop-harvesting in the Punjab region.
Vaisakhi is the most important festival in the Sikh calendar, taking place on the first lunar month of Vaisakh, which falls on 14 April each year. On this day, the Khalsa was created and much celebration takes place in the form of Samagams, Nagar Kirtan, Gatka exhibitions, Akand Paths and so on.
On the 16th of this month, Guru Angad and Guru Har Krishan took leave for their higher abode and passed the Guruship to Guru Amar Das and Guru Tegh Bahadur respectively.Moreover, on the 18th, the Sikhs celebrate the birthday of Guru Angad Dev (the second Sikh Guru) and Guru Tegh Bahadur (the ninth Sikh Guru).