[1] The best-known and most significant example today is the liturgical Paschal Triduum (the three days from the evening of Maundy Thursday to Easter Sunday).
In Eastern Christianity (both Orthodox and Catholic) the analogues of festive tridua take the form of a major feasts followed by an associated Synaxis.
A triduum was held in Limerick in 1867 in honor of Our Lady of Perpetual Succour, at which the associated icon was first displayed for public veneration in Ireland.
[2] In January of 1915, a number of German cities observed a triduum of meditation on World War I, an event which was influential on a young Martin Heidegger.
[3] James G. McGarry, a Catholic priest and professor, organized a 1977 triduum observance at Knock Shrine.