World Day for Cultural Diversity for Dialogue and Development

World Day for Cultural Diversity for Dialogue and Development (International)

Navy Day (Chile)

Navy Day (Chile)

International Tea Day

International Tea Day (International)

Armed Forces Day

Day of Patriots and Military (Hungary)

Circassian Day of Mourning

Circassian Day of Mourning (Circassians)

May 21 (Eastern Orthodox liturgics)

Christian feast day:
May 21 (Eastern Orthodox liturgics)

Saints of the Cristero War

Christian feast day:
Saints of the Cristero War, including Christopher Magallanes

John Eliot (missionary)

Christian feast day:
John Elliot (Episcopal Church)

Beatification

Christian feast day:
Blessed Hemming of Turku

Helena, mother of Constantine I

Christian feast day:
Helena of Constantinople, also known as "Feast of the Holy Great Sovereigns Constantine and Helen, Equal-to-the-Apostles." (Eastern Orthodox Church, Anglican Communion)

Eugène de Mazenod

Christian feast day:
Eugène de Mazenod

Feast of Corpus Christi

Christian feast day:
Earliest day on which Corpus Christi can fall, while June 24 is the latest; held on Thursday after Trinity Sunday (often locally moved to Sunday). (Roman Catholic Church)

Franz Jägerstätter

Christian feast day:
Blessed Franz Jägerstätter

Beatification

Christian feast day:
Blessed Adílio Daronch and Manuel Gómez González

Afro-Colombian Day

Afro-Colombian Day (Colombia)