January 15 day of week Monday
Holidays and observances
Arbor Day (Egypt)
Armed Forces Remembrance Day (Nigeria)
Army Day (India)
Christian feast day:
Abeluzius (Ethiopian Orthodox Tewahedo Church)
Arnold Janssen
Francis Ferdinand de Capillas (one of Martyr Saints of China)
Ita
Our Lady of the Poor
Macarius of Egypt (Western Christianity)
Maurus and Placidus (Order of Saint Benedict)
Paul the Hermit
January 15 (Eastern Orthodox liturgics)
Earliest day on which Martin Luther King Jr. Day can fall (the 15th being his birthday), while January 21 is the latest; celebrated on the third Monday in January. (United States)
Earliest day on which Sinulog Festival can fall, while January 21 is the latest; celebrated on the third Sunday in January. (Philippines)
John Chilembwe Day (Malawi)
Korean Alphabet Day (North Korea)
Ocean Duty Day (Indonesia)
Sagichō at Tsurugaoka Hachimangū. (Kamakura, Japan)
Teacher's Day (Venezuela)
Black Christ of Esquipulas day 
The second day of the sidereal winter solstice festivals in India (see January 14):
Thai Pongal, Tamil harvest festival
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