Days of Military Honour

Victory over the Golden Horde in the Battle of Kulikovo (Russia)

Spring day

Student's Day (Bolivia)

International Day of Peace

International Day of Peace (International)

Founders' Day (Ghana)

Founder's Day and National Volunteer Day (Ghana)

Public holidays in Poland

Customs Service Day (Poland)

Proclamation No. 1081

Commemoration of the Declaration of Martial Law (Philippines)

Arbor Day

Arbor Day (Brazil)

September 21 (Eastern Orthodox liturgics)

Christian feast day:
September 21 (Eastern Orthodox liturgics)

Nativity of Mary

Christian feast day:
Nativity of the Theotokos (Eastern Orthodox Church, Julian calendar)

Maura of Troyes

Christian feast day:
Maura of Troyes

Matthew the Apostle

Christian feast day:
Matthew the Evangelist (Western Church)

Laurent-Joseph-Marius Imbert

Christian feast day:
Laurent-Joseph-Marius Imbert (one of the Korean Martyrs)

Ephigenia of Ethiopia

Christian feast day:
Ephigenia of Ethiopia

Cadoc

Christian feast day:
Cadoc

Spring day

Autumnal equinox observances in the Northern Hemisphere, vernal equinox observances in the Southern Hemisphere (see September 22):
Spring Day (Argentina)