A triduum is a religious observance lasting three days.John Wynne, "Triduum"in The Catholic Encyclopedia (New York 1912)

Triduum
Triduum
Triduum
?wi?te Triduum Paschalne
The Triduum: Mar. 29 - 31, 2018
Temporale EPB-29 Triduum
Holy Week - The Triduum: Apr. 13-15, 2017
Celebrating the Easter Triduum with children
The three days : parish prayer in the Paschal triduum
Listening concepts under extreme acoustic conditions in anechoic and reverberation chambers and underwater during aXes-Triduum of Ne...