Holy Days of obligation
Sundays and holy days of obligation are days on which the failthful are obliged to participate in the Mass [... and to] abstain from those works and affairs which hinder the worship to be rendered to God, the joy proper to the Lord's day, or the suitable relaxation of mind and body (Code of Canon Law, Canon 1247).
Holy days mark days in the liturgical year of special importance or that merit special celebration. Worldwide, there is some variation in the dates of celebration of holy days as local Church authorities acknowledge patron saints or allow the celebration of holy days that occur during the week on the nearest Sunday. In England and Wales, according to a 1984 decision of the Bishops' Conference, holy days which fall on Saturday or Monday are in general transferred to the Sunday. From the first Sunday of Advent 2006 the feasts of The Epiphany of the Lord, The Ascension of the Lord and the Body and Blood of Christ have also routinely been transferred to the neighbouring Sunday.
The table below, copied from the website of the Liturgy Office of England and Wales, lists the dates of holy days (in bold) and some other significant dates during the years 2011-2015.
| 2011 | 2012 | 2013 | 2014 | 2015 | |
| Lectionary (Sunday/Weekday) | A/I | B/II | C/1 | A/II | B/I |
| First Sunday of Advent | 28 November 2010 | 27 November 2011 | 2 December 2012 | 1 December 2013 | 30 November 2014 |
| Birth of the Lord | 25 December | 25 December | 25 December | 25 December | 25 December |
| Epiphany | 2 January | 8 January | 6 January | 5 January | 4 January |
| Ash Wednesday | 9 March | 22 February | 13 February | 5 March | 18 February |
| Easter Sunday | 24 April | 8 April | 31 March | 20 April | 5 April |
| Ascension | 5 June | 20 May | 12 May | 1 June | 17 May |
| Pentecost | 12 June | 27 May | 19 May | 8 June | 24 May |
| The Body and Blood of Christ | 26 June | 10 June | 2 June | 22 June | 7 June |
| St Peter & St Paul | 29 June | 29 June | 30 June | 29 June | 28 June |
| Assumption | 14 August | 15 August | 15 August | 15 August | 16 August |
| All Saints | 1 November | 1 November | 1 November | 2 November | 1 November |
| First Sunday of Advent | 27 November | 2 December | 1 December | 30 November | 29 November |
Liturgical Calendar from the Liturgy Office of England and Wales