Clean Monday

Etymology
From the Old Testament reading at sext on this day, Isaiah 1:16, “Wash you, make you clean; put away the evil of your doings from before mine eyes; cease to do evil...”

Proper noun

 * 1)  The seventh Monday before Easter,  traditionally regarded as the beginning of Lent

Usage notes
In the Greek and most other denominations of Eastern Orthodoxy, the liturgical day is reckoned according to Jewish practice and so begins at the vespers service on the preceding Sunday evening.

Translations

 * Greek:
 * Russian: Чи́стый понеде́льник