Roman Catholics, Anglicans, Eastern Christians, and traditional Protestant groups center their worship around a liturgical calendar. Some events that are part of this calendar are the "holy days", such as solemnities which honor an event in the life of Jesus or the saints, times of fasting such as Lent, and other events, such as memoria. Christian groups that do not follow a liturgical tradition often keep some celebrations, such as Christmas, Easter,and Pentecost. A few churches do not use a liturgical calendar.