Paschal Triduum
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). Other liturgical tridua celebrated in Western Christianity include the Rogation Days preceding Ascension Thursday, the feasts of Christmas, Easter and Pentecost together with the first two days of their octave, and Allhallowtide that lasts from Halloween to All Souls Day.