The  Roman Catholic Church in a number of countries that do not observe the feast as a public holiday has obtained permission from the Vatican to move observance of the Feast of the Ascension from the traditional Thursday to the following Sunday, the Sunday before  Pentecost. This is in keeping with a trend to move  Holy Days of Obligation from weekdays to Sunday, to encourage more Christians to observe feasts considered important. The decision to move a feast is made by the bishops of an  ecclesiastical province, i.e. an  archbishop and the neighbouring bishops. The switch to Sunday was made in 1992 by the  church in Australia; before 1996 in parts of Europe;  in 1996 in  Ireland; before 1998  in Canada and parts of the western United States; in many other parts  in the United States from 1999; and in  England and Wales from 2007. The U.S. ecclesiastical provinces which retain Thursday observance in 2009 are  Boston,  Hartford,  New York,  Newark,  Omaha, and  Philadelphia. When celebrated on Sunday, the earliest possible date is May 3, and the latest is June 6.

     The observance of this feast is of great antiquity.  Eusebius seems to hint at the celebration of it in the 4th century. At the beginning of the 5th century,  St. Augustine says that it is of  Apostolic origin, and he speaks of it in a way that shows it was the universal observance of the Church long before his time. Frequent mention of it is made in the writings of  St. John Chrysostom,  St. Gregory of Nyssa, and in the  Constitution of the Apostles. The Pilgrimage of Aetheria speaks of the vigil of this feast and of the feast itself, as they were kept in the church built over the grotto in  Bethlehem in which Christ was born. It may be that prior to the 5th century the fact narrated in the Gospels was commemorated in conjunction with the feast of Easter or Pentecost. Some believe that the much-disputed forty-third decree of the  Synod of Elvira (c. 300) condemning the practice of observing a feast on the fortieth day after Easter and neglecting to keep Pentecost on the fiftieth day, implies that the proper usage of the time was to commemorate the Ascension along with Pentecost. Representations of the mystery are found in diptychs and  frescoes dating as early as the 5th century.