Responsories for Holy Week Maundy Thursday and Good Friday respectively, rather than on a sequence of names referring to Maundy Thursday, Good Friday and Holy Saturday respectively. The responsories following each lesson of these matins (so also 27) were usually sung, and these are the Tenebrae Responsoria, or the Responsories for Holy Week. The name of a collection of such responsories may also refer to the Holy Triduum, as in Orlande de Lassus' "". Maundy Thursday is the fifth day of the Holy Week (Latin: Feria V or Feria Quinta). In Latin the feast is also indicated as "In Cœna Domini" ("At the meal
Eight-day week popularity of the seven-day rhythm won and the eight-day week disappeared. The cycle of seven days, named after the sun, the moon, and the five planets visible to the naked eye, was already customary in the time of Justin Martyr, who wrote of the Christians meeting on the Day of the Sun (Sunday). Emperor Constantine eventually established the seven-day week in the Roman calendar in AD 321. The Celts used periods of darkness such as night and winter to begin their calculations of time. This meant that the first period of time in a "week" was a night, followed by