Punjabi calendar
The Punjabi calendar is a luni-solar calendar used by the Punjabi people in Punjab, and around the world. Punjabi Muslims use the calendar for agricultural purpose as it correspond well with the climate and seasons of Punjab while Hindus and Sikhs also use it for religious purposes.
Punjabi Hindus also use the Bikrami calendar which is the basis of this calendar. Sikhs followed the Bikrami calendar but since 2003 the Nanakshahi calendar, which uses the tropical years which keeps the calendar aligned with the western Gregorian calendar, has been used. The Nanakshahi calendar was adopted by the Shiromani Gurudwara Parbandhak Committee for Sikhs in 1999. The dates of festivals based on the Nanakshahi calendar are always fixed.
Punjabi Muslims also use the Hijri calendar alongside the Punjabi calendar for religious purposes. Many festivals in Punjab, Pakistan are determined by the Punjabi calendar, such as Muharram which is observed twice, once according to the Muslim year and again on the 10th of Harh/18th of Jeth. The Punjabi calendar is the one the rural population follows in Pakistani Punjab.
In Punjab though the solar calendar is generally followed, the lunar calendar used is purṇimānta, or calculated from the ending moment of the full moon: the beginning of the dark fortnight. Chait is considered to be the first month of the lunar year. The lunar year begins on Chet Sudi: the first day after the new moon in Chet. This means that the first half of the purṇimānta month of Chaitra goes to the previous year, while the second half belongs to the new Lunar year.
The Punjabi solar new year starts on the first of Vaisakh. The day is considered from sunrise to next sunrise and for the first day of the solar months, the Orissa rule is observed: day 1 of the month occurs on the day of the transition of monthly constellations, or sangrānd in Punjabi.
The traditional lunisolar Punjabi Bikrami calendar uses the sidereal year. The Bikrami calendar days are based on the lunar phases called tithis, thus the festivals based on the Bikrami calendar fluctuate.
Instead of celebrating the new-year on Chet 1 as is the case with the Nanakshahi calendar of Sikhism, the Punjabi peasantry found it more convenient to celebrate their new-year on Vaisakh 1 to coincide with their harvest's due-date.