Shunbun no Hi “Vernal Equinox Day”. March 20-21. Shunbun no Hi wa itsu desu ka? “When is Vernal Equinox Day?”. This holiday is celebrated on March 20 or 21, a day where the sun crosses the equator making night and day equal in length. Shunbun no Hi wa nandesu ka? “What is Vernal Equinox Day?”.