Ordinary Time is a season of the Christian liturgical calendar, particularly the calendar of the ordinary form of the Roman rite of the Catholic Church, although some other rites in Western Christianity also use this term. The English name "ordinary time" translates the Latin term Tempus per annum (literally "time through the year"). Since 1970 in the ordinary form of the Roman rite in the Catholic Church, Ordinary Time comprises two periods: one beginning on the day after the Feast of the Baptism of the Lord (the end of the Christmas season) and ending on the day before Ash Wednesday, the other beginning on the Monday after Pentecost (the conclusion of Eastertide) and continuing until the Saturday before Advent Sunday (the First Sunday of Advent). The Church numbers the weeks of Ordinary Time, although several Sundays bear the names of feasts or solemnities celebrated on those days, including Trinity Sunday and the Feast of Christ the King.
Periods of Ordinary Time 
In the Catholic Church, Ordinary Time begins on the day following the Feast of the Baptism of the Lord. The Church normally celebrates this feast on the Sunday after Solemnity of the Epiphany of the Lord (6 January). Some dioceses, including those in the United States of America, however, always celebrate Epiphany on the Sunday after Solemnity of Mary, Mother of God (1 January); when they celebrate Solemnity of the Epiphany of the Lord on Sunday 7 or 8 January, they move the Feast of the Baptism of the Lord to Monday 8 or 9 January, respectively. Therefore, Ordinary Time starts on Tuesday 9 or 10 January in those years and dioceses. The Christmas season includes the Feast of the Baptism of the Lord, so Ordinary Time begins the next day (Monday or Tuesday, not on Sunday); however, the Sunday after the Feast of the Baptism of the Lord always counts as the "Second Sunday of Ordinary Time."
Ordinary Time continues through the day before Ash Wednesday, which falls between 4 February and 10 March (inclusive) and marks the beginning of the Season of Lent. Thus for Roman Catholics, the period of Ordinary Time between Christmas and Lent may end amid the fourth, fifth, sixth, seventh, eighth, or ninth week of Ordinary Times. Ash Wednesday is a moveable feast, which occurs on the fortieth day (excluding Sundays) before the Solemnity of the Resurrection of the Lord (Easter Sunday).
In the Church of England, Ordinary Time begins on the day after Feast of the Presentation of the Lord (2 February) and continues until Ash Wednesday. The first period of Ordinary Time is somewhat shorter than its Catholic counterpart; indeed, it may be as short as a single day if Ash Wednesday falls on its earliest possible date of 4 February.
Ordinary Time resumes on the Monday following Solemnity of Pentecost, the Sunday between 10 May and 13 June that marks the fiftieth day of Easter. Ordinary Time concludes with the Saturday afternoon before the first Sunday of Advent (27 November to 3 December). Ordinary Time thus always includes the entire months of July, August, September and October and most or all of June and November; in some years, Ordinary Time includes a portion of May, a day or two in early December, or both. The Catholic Church substitutes the Solemnity of Our Lord Jesus Christ the King of the Universe in the place of the 34th Sunday in Ordinary Time, the last Sunday of the season.
The actual number of complete or partial weeks of Ordinary Time in any given year can total 33 or 34. In most years, Ordinary Time comprises only 33 weeks, so the Church omits one week that otherwise would precede the resumption of Ordinary Time following Pentecost Sunday. For example, in 2011, the Sunday before Ash Wednesday was the 9th Sunday in Ordinary Time, but the day after Pentecost Sunday began the 11th Week in Ordinary Time.
In the Church of England, a similar situation arises with "Sundays after Trinity", as Sundays in the second period of Ordinary Time are termed (until the final four, which are termed "Sundays before Advent"). The total number of Sundays varies according to the date of Easter and can number anything from 18 to 23. When there are 23, the Collect and Post-Communion for the 22nd Sunday are taken from the provision for the Third Sunday before Lent.
Solemnities and feasts within Ordinary Time 
|Weeks of Ordinary Time|
In addition, certain solemnities and feasts that fall on Sundays during Ordinary Time preempt the observance of an ordinarily numbered Sunday. On preempted Sundays, the liturgical color of the feast or solemnity replaces the liturgical color green. These feast days include, in the Roman Catholic calendar, any holy day of obligation, any other solemnity, any feast of the Lord, and the Commemoration of All Faithful Departed Souls. On the universal calendar, these include:
- Feast of the Presentation of the Lord on 2 February (liturgical color: white),
- Solemnity of the Nativity of Saint John the Baptist on 24 June (liturgical color: white),
- Solemnity of Saints Peter and Paul on 29 June (liturgical color: red)
- Feast of the Transfiguration of the Lord on 6 August (liturgical color: white)
- Feast of the Exaltation of the Holy Cross on 14 September (liturgical color: red)
- Solemnity of All Saints on 1 November (liturgical color: white)
- Commemoration of All Faithful Departed Souls on 2 November (liturgical color: violet or black), and
- Feast of the Dedication of the Basilica of Saints John Lateran in Rome on 9 November (liturgical color: white).
The following observances always preempt a Sunday in Ordinary Time:
- Feast of the Baptism of the Lord or Solemnity of the Epiphany of the Lord always preempts the First Sunday in Ordinary Time
- Solemnity of Pentecost always begins the first week of Ordinary Time after Eastertide
- Solemnity of the Most Holy Trinity always preempts the Sunday immediately after Pentecost
- Solemnity of Our Lord Jesus Christ the King of the Universe always preempts the 34th (and final) Sunday in Ordinary Time
Other solemnities which outrank Sundays of Ordinary Time vary from parish to parish and diocese to diocese; they may include the feast of the patron saint of a parish and the feast of the dedication of the parish church.
In addition, if a solemnity or feast that outranks a Sunday of Ordinary Time, such as those mentioned above, should occur during the week, a priest celebrating Mass with a congregation may observe the solemnity on a nearby Sunday. Such a celebration is traditionally called an "external solemnity," even if the feast in question is not ranked as a solemnity. If an external solemnity is celebrated on a Sunday, the color of that celebration is used rather than green.
Use of the term 
Before the liturgical reforms of 1970, there were two distinct seasons in the Roman Breviary and Roman Missal, known as the season after Epiphany and the season after Pentecost, respectively. Liturgical days in these times were referred to as the -nth Sunday after Epiphany or Pentecost, or Feria II,III,IV,V or VI after the -nth Sunday. With the reforms came the introduction of four liturgical weeks, the 6th through 9th weeks of Ordinary Time, which could fall either after Epiphany or after Pentecost, making the old numbering scheme unusable, and the term tempus per annum was used to describe both of these seasons. Before the reforms until the present, the term tempus per annum has been used to describe the season of the Little Office of the Blessed Virgin Mary that is not part of Advent or Christmastide, and so tempus per annum extends from Matins on 3 February through None on the last Saturday before Advent.
Kingdomtide exception 
See also 
- Lectionary Calendar and Movable Feasts
- There are 34 weeks of Ordinary Time in years with dominical letters A or g or some combination containing A or g, i.e., Ag, bA, or gf. All other years have 33 weeks of Ordinary Time, with the 5th, 6th, 7th, 8th, 9th, or 10th week dropped from the calendar that year.
- In the United States, white may be used in place of violet on All Souls Day.