The Punjabi year runs Chet, Vaisakh, Jeth, Harh, Sawan, Bhadon, Assu, Katak, Maghar, Poh, Magh, Phagun, beginning in the middle of March.
Each month has a character in the literature. The Barah Maha, the poem of twelve months, is a Punjabi form in which a woman describes the year through her separation from her beloved, and it exists in versions by Guru Nanak Dev Ji and Guru Arjan Dev Ji in the Guru Granth Sahib Ji and by many later poets.
Sawan is the monsoon and the month of swings and of women returning to their parents' homes. Poh and Magh are the cold. Harh is the worst heat. Chet is the start.
The sangrand, the first day of each month, is observed in gurdwaras with the reading of the relevant Barah Maha stanza.
Older farmers reckon sowing and harvest by these months and not by the Gregorian calendar, and the agricultural extension literature is published with both.
The Nanakshahi calendar of 2003 took its month names from the Barah Maha, which is why a modern reform calendar is named for a sixteenth-century poem.
The desi months are lunar-solar and the agricultural year runs on them: sowing, harvest, fairs and marriages are all dated by them rather than by the Gregorian calendar.
Vaisakhi falls on the first of Vaisakh and is the solar new year, which is why it is marked across the subcontinent under different names on the same day.
The Nanakshahi calendar adopted in 2003 fixed the Sikh anniversaries to the solar year, and the disagreement over it since is a disagreement about which calendar the community lives by.