Baisakhi marks the jubilation of a plentiful harvest and is celebrated on the first day of the month of Baisakh (April/May). This is the New Year's Day, going by the Saka calendar and corresponds to April 13th of the Gregorian calendar.
Essentially, a North Indian harvest festival, it is the time for the reaping of the rabi (winter crop). Joyful Punjabis perform Bhangra to dholak and enact the complete process of agriculture from the tilling of the soil through harvesting.
For the Sikhs, the day has great spiritual meaning as Guru Gobind, the 10th guru of Sikhs, established Khalsa was on this day at Anandpur in 1699 AD.
The Sikhs were baptized to form the Elect. This baptism of the sword, called pahul, led to the creating of the Panj Pyare, the Beloved Five. Each Khalsa was to adopt the panch kakkas, (the five K's), Kesh (unshorn hair), kanga (small boxwood comb in their hair), kaccha (a pair of shorts), kara (a steel bangle), and a kirpan (a short dagger), which have since become an integral part of the Sikh identity.