Aliturgical days

Aliturgical Days are days in the Christian liturgical year when mass is not celebrated.[1]

Latin rite

In the Latin liturgical rites the only fully aliturgical day is Good Friday. Because of this, a specific mass known as the Mass of the Presanctified is used.[2]

Byzantine rite

A Russian Orthodox priest during a Presanctified Liturgy

In the Byzantine rite used by the Eastern Orthodox Church and Byzantine Catholic Churches there multiple aliturgical days beyond Good Friday. During Great Lent, it is forbidden to consecrate a new Eucharist, so the Liturgy of the Presanctified Gifts is used, where a previously consecrated host is used.

References

1. Thurston, Herbert (1907). "Aliturgical Days" . In Herbermann, Charles (ed.). Catholic Encyclopedia. Vol. 1. New York: Robert Appleton Company.
2. Oxford Reference website, Mass of the Presanctified