The Apostles’ Fast
The beginning of the Apostles’ Fast – the Monday after All Saints – is based on the moveable Paschalion, and can begin as early as May 18, and as late as June 21. But its end, being fixed by the feast of the Apostles Peter and Paul, has no earliest/latest dates: the Fast always ends on June 29. Therefore its length varies from 8 to 42 days.
All these diagrams follow the traditional (or Julian or Old) festal Calendar of the Orthodox Church. When the moveable Paschalion follows the Julian Calendar, but the immovable Menaion feasts follow the Gregorian (or New), the Menaion feasts fall 13 days later than they are intended to do when used with the Paschalion. Because of this, in any year that the Apostles’ Fast is 13 days or shorter, it disappears when the Menaion feasts are celebrated according to the Gregorian Calendar.