Vaishakha (Marathi: वैशाख) or Baisakha (Hindi: बैसाख) (Nepali: बैशाख) is a month of the Hindu calendar that corresponds to April/May in the Gregorian Calendar. In the Indian national calendar Vaisakha is the second month of the year. It is the first month of the Nepali calendar (the Vikram Samvat), Punjabi calendar and the Bengali calendar (where it is called Boishakh). Regional calendars used on the sub-continent have two aspects: lunar and solar. Lunar months begin with Chaitra and solar months start with Vaisakha Sankranti. However, regional calendars mark one one official new year is celebrated. In regions such as Maharashtra which begin the official new year with the commencement of the lunar year, the solar year is marked by celebrating Vaisakha Sankranti. Conversely, regions starting the new year with Vaisakha Sankranti, give prominence to the start of the lunar year in Chaitra.
In the Hindu solar calendar, Vaisakha begins in mid-April in Bengal, Nepal and Punjab. In Tamil Nadu, it is known as Vaikasi and represents the second month of the Tamil solar calendar. In the Hindu lunar calendar, Vaisakha begins with the new moon in April and represents the second month of the lunar year. The name of the month is derived from the position of the Sun near the star Vishakha. In the Vaishnava calendar, Madhusudana governs this month.
The month of Boishakh also marks the official start of Summer. The month is notorious for the afternoon storms called Kalboishakhi (Nor'wester). The storms usually start with strong gusts from the north-western direction at the end of a hot day and cause widespread destruction.
The first day of Baishakh is celebrated as the Pôhela Boishak or Bangla New Year's Day. The day is observed with cultural programs, festivals and carnivals all around the country. The day of is also the beginning of all business activities in Bangladesh and neighboring Indian state of West Bengal. The traders starts new fiscal account book called Halkhata. The accounting in the Halkhata begins only after this day. It is celebrated with sweets and gifts with customers.
Vaisakha Purnima is celebrated as Buddha Purnima or the birthday of Gautama Buddha amongst southern Buddhists or the Theravada school. Purnima refers to the Full Moon. Known in Sinhalese as Vesak, it is observed in the full moon of May.