Feast of the Ascension term "Holy Thursday" to mean Ascension Day is rare, and the term is more generally applied by most Christian denominations to Maundy Thursday in Holy Week. In Western Christianity, the earliest possible date is April 30 (as in 1818 and 2285), the latest possible date is June 3 (as in 1943 and 2038). In Roman Catholicism, the Ascension of the Lord is a Holy Day of Obligation and in the Anglican Communion, Holy Thursday is a Principal Feast. The three days before Ascension Thursday are sometimes referred to as the Rogation days, and the previous Sunday — the Sixth Sunday
Armelin's calendar mind of modest ability will learn in a few minutes the weekday with which each month invariably begins, and will be able to compute quickly the day of the week upon which any day of any month falls. Each stated holiday falls upon its invariable day of the week. Thanksgiving Day falls always on November 30. A major disadvantage is for sabbatarians, who are obliged to worship every seventh day. Their holy day will occur on a different weekday every year. Armelin's project received the first premium of the French Astronomical Society. The World Calendar, roughly identical, has been promoted