Boishakh Mash—also known as Baisakh or Baishakh—opens Bengali Calendar 1433 in mid-April 2026, setting the cultural and seasonal tone for West Bengal and Bangladesh. This guide clarifies region-specific dates (15 April–15 May in West Bengal; 14 April start in Bangladesh), explains the sidereal solar mechanics behind Mesha Saṅkrānti, and shows how time zones and civic…