In the Western Christian calendar, Ash Wednesday is the first day of Lent and occurs forty-six days before Easter. It falls on different dates from year to year, according to the date of Easter; it can occur as early as February 4 or as late as March 10.

At Masses and services of worship on this day, ashes are imposed on the foreheads (or tonsure spots, in the case of some clergy) of the faithful. The priest, minister, or in some cases officiating layperson marks the forehead of each participant with black ashes, in the shape of a cross, which the worshiper traditionally retains until washing it off after sundown. The symbolism echoes the ancient Near Eastern tradition of throwing ash over one's head signifying repentance before God (as related in the Bible). The priest or minister offers the worshiper an instruction while applying the ashes. These are three examples:

Remember that you are dust, and unto dust you shall return.

– God, Genesis 3:19

Turn away from sin and be faithful to the Gospel.

– Jesus, Mark 1:15

Repent, and hear the good news.

– Jesus, Mark 1:15