The holy season of Lent begins on February 25, with the Divine Liturgy, and Imposition of Ashes. The service will begin at 7:00 p.m.

From Father John Fenton in an article from 2012:

For Byzantine Orthodox Christians, the First Day of the Great Fast is on the Monday before the First Sunday in Lent; and for Western Orthodox Christians the Lenten fast begins on the Wednesday before, commonly known as Ash Wednesday.

While both traditions observe a 40 day fast, the different starting dates for the fast are related to how the fast is calculated. Early on in the West, the Lenten included every day including Saturdays but never included Sundays. Therefore, in order to achieve 40 days, since the 7^thcentury the Western Orthodox have fast not only for six fully weeks (i.e., 36 days) but also four additional days. Hence, for about 1400 years the Lenten fast in the West has begun on the Wednesday before the First Sunday in Lent.

It is not clear when the Wednesday beginning the Lenten fast began to include the imposition of ashes. Originally, the imposition of ashes was one of several public rites required of those penitents who wished to be restored to the church. As early as the 4^th century, these rites were associated with a 40 day fast. Most likely this fast was the Lenten fast, but the evidence is too thin to be conclusive. What does seem clear is that, by the end of the 10^th century, it was customary in Western Europe (but not yet in Rome) for all the faithful to receive ashes on the first day of the Lenten fast. In 1091, this custom was then ordered by Pope Urban II at the council of Benevento to be extended to the church in Rome. Not long after that, the name of the day was referred to in the liturgical books as “Feria Quarta Cinerum” (i.e., Ash Wednesday).

The ashes that are placed on the heads of the faithful are made from burning the blessed palm branches from the previous year’s Palm Sunday. Parishioners are taught to place these blessed palms behind crucifixes and icons in their homes throughout the year, and then return them to the parish church during the weeks before Ash Wednesday. After they are burned, the ashes are then blessed by the priest, usually immediately before the Ash Wednesday mass.

While they may be distributed outside of the mass or any liturgical service, commonly the faithful receive their ashes immediately before the Ash Wednesday mass. As the choir sings various chants, the priest places the ashes on each person while saying, “Remember, man that thou art dust, and unto dust thou shalt return.” (Gen 3.19) These words indicate that the ashes are a sign of mortality, and thereby spiritually call each person to mortify their flesh during the season of Lent through the sacrificial acts of prayer, fasting, almsgiving. In fact, the Scripture readings for the Ash Wednesday mass say as much. From the prophet Joel, the faithful hear that they are to return to the Lord with all their heart by means of fasting, weeping, and mourning; and in this way, they rend their hearts and turn to the Lord God. Likewise, in the Gospel lesson the Lord admonishes the faithful to fast in order to recall that their hearts are to be fixed not on earthly but heavenly treasures.

For Western Orthodox Christians, the reception of ashes together as a community on the first day of the Lenten fast is a tactilely poignant sign that their fast is not simply the denial of foods, but the ascetic discipline of subduing the passions and putting to death ungodly ways so that they may strive to attain, with repentant joy, not only the great celebration both of the Queen of feasts, but also the heavenly riches and abundant life that await those who remain faithful in word and deed.