In the Christian (Eastern) Orthodox Church, Great Lent marks the forty days leading to the death and resurrection of Jesus Christ (the 40 days before Holy Week, which is the week when Christian Orthodox followers remember Christ's Passion, Death and Resurrection). The first day of Great Lent is called Clean Monday. Clean Monday marks the beginning of 40 days of fasting, intensified prayer, penance, and almsgiving. Many mark the beginning of Great Lent on Sunday night or Monday at a special church service asking for forgiveness in the Christian Orthodox Church https://provost.umich.edu/