Do you know what a clean Monday for Christians is?

The first day of great Lent for Eastern and Orthodox Catholics.

For Western Christians, especially Roman Catholics, Lutherans and members of the Anglican communion, Lent begins with Ash Wednesday. For Catholics in Eastern rites, however, Lent has already begun when Ash Wednesday arrives.

What is clean Monday?
Clean Monday is the first day of Great Lent, as Eastern Catholics and Eastern Orthodox refer to the Lent season. For both Eastern Catholics and Eastern Orthodox, clean Monday falls on the Monday of the seventh week before Easter Sunday; for Eastern Catholics, which places a clean Monday two days before Western Christians celebrate Ash Wednesday.

When is Monday clean for Eastern Catholics?
Therefore, to calculate the clean Monday date for Eastern Catholics in a given year, you simply need to take the Ash Wednesday date in that year and subtract two days.

Do Eastern Orthodox celebrate clean Monday on the same day?
The date on which Eastern Orthodox celebrate clean Monday is usually different from the date on which Eastern Catholics celebrate it. This is because the clean Monday date depends on the Easter date and the Eastern Orthodox calculate the Easter date using the Julian calendar. In the years when Easter falls on the same day for both Western Christians and Eastern Orthodox (such as 2017), clean Monday also falls on the same day.

When is Monday clean for Eastern Orthodox?
To calculate the clean Monday date for the Eastern Orthodox, start with the Eastern Orthodox Easter date and count back seven weeks. The clean Monday of the Eastern Orthodox is the Monday of that week.

Why is Clean Monday sometimes called Ash Monday?
Clean Monday is sometimes called Ash Monday, especially among Maronite Catholics, an Eastern Catholic rite rooted in Lebanon. Over the years, Maronites have adopted the Western habit of distributing ashes on the first day of Lent, but since Great Lent began for Maronites on clean Monday instead of Ash Wednesday, they have distributed the ashes on clean Monday, and so they started calling Ash Monday. (With minor exceptions, no other Eastern Catholic or Eastern Orthodox distributes ash on Clean Monday.)

Other names for clean Monday
In addition to Ash Monday, Clean Monday is known by other names among several Eastern Christian groups. Pure Monday is the most common name; Among Catholics and Greek Orthodox, clean Monday is referred to by its Greek name, Kathari Deftera (just like Shrove Tuesday is simply French for "Shrove Tuesday"). Among Eastern Christians in Cyprus, clean Monday is called green Monday, a reflection of the fact that clean Monday has traditionally been regarded by Greek Christians as the first day of spring.

How is clean Monday observed?
Clean Monday reminds us that we should start Lent with good intentions and with the desire to clean our spiritual home. Clean Monday is a strict fasting day for Eastern Catholics and Eastern Orthodox, including abstinence not only from meat but also from eggs and dairy products.

On clean Mondays and throughout Lent, Eastern Catholics often pray the prayer of St. Ephrem the Syrian.