General Roman Calendar

The General Roman Calendar is the liturgical calendar that indicates the dates of celebrations of saints and mysteries of the Lord (Jesus Christ) in the Roman Rite of the Catholic Church, wherever this liturgical rite is in use. These celebrations are a fixed annual date, or occur on a particular day of the week. Examples are the Feast of the Baptism of the Lord in January and the Feast of Christ the King in November.
Others relate to the date of Easter. Examples are the celebrations of the Sacred Heart of Jesus and the Immaculate Heart of Mary. National and diocesan calendars, including that of the diocese of Rome itself as well as the calendars of religious institutes and even of continents, add other saints and mysteries or transfer the celebration of a particular saint or mystery from the date assigned in the General Calendar to another date.
These liturgical calendars indicate the degree or rank of each celebration: memorial (which can be merely optional), feast, or solemnity. Among other differences, the Gloria is said or sung at the Mass of a feast but not at that of a memorial. The Creed is added on solemnities.
The last general revision of the General Roman Calendar was in 1969 and was authorized by the motu proprio "Mysterii Paschalis" of Paul VI. The motu proprio and the decree of promulgation were included in the book "Calendarium Romanum", published in the same year by Libreria Editrice Vaticana. This contained the official document "Universal Norms on the Liturgical Year and the Calendar", and the list of celebrations of the General Roman Calendar. Both these documents are printed, in their present revised form, in the "Roman Missal", after the "General Instruction of the Roman Missal".
Selection of saints included.
While canonization involves the addition of the saint's name to the Roman Martyrology, it does not necessarily involve the insertion of the saint's name into the General Roman Calendar, which mentions only a very limited selection of canonized saints. There is a common misconception that certain saints, (e.g., Christopher) were "unsainted" in 1969 or that veneration of them was "suppressed". Christopher is recognized as a saint of the Catholic Church, being listed as a martyr in the Roman Martyrology under 25 July. 
In 1969, Paul VI issued the motu proprio "Mysterii Paschalis". In it, he recognized that, while the written "Acts of Saint Christopher" are merely legendary, attestations to the veneration of the martyr date from ancient times. His change in the calendar of saints included "leaving the memorial of Saint Christopher to local calendars", because of the relatively late date of its insertion into the Roman calendar.
Liturgical year.
In the liturgical books, the document "General Roman Calendar", which lists not only fixed celebrations but also some moveable ones, is printed immediately after the document "Universal Norms on the Liturgical Year and the Calendar", which states that "throughout the course of the year the Church unfolds the entire mystery of Christ and observes the birthdays of the Saints". The birth of a saint to heaven is as a rule celebrated on a fixed day of the year. Sometimes they may be moved either to or from a Sunday. The mysteries of Christ are often celebrated on dates that always vary from year to year.
The Catholic Church's year combines two cycles of liturgical celebrations. One has been called the Proper of Time or Temporale, associated with the moveable date of Easter and the fixed date of Christmas. The other is associated with fixed calendar dates and has been called the Proper of Saints or Sanctorale. The General Roman Calendar includes celebrations that belong to the Proper of Time or Temporale and is not limited to those that make up the Proper of Saints or Sanctorale. An instance where two observances occur on the same date is called an occurrence.
Transfer of celebrations.
Some celebrations listed in the General Roman Calendar are transferred to another date:
List of celebrations inscribed in the GRC.
This list contains all celebrations currently inscribed in the General Roman Calendar. It is updated whenever the pope makes changes to the celebrations in the General Roman Calendar.
When no citation is provided for a particular celebration, it comes from "Calendarium Romanum Generale" (General Roman Calendar) as printed in the Latin original of Roman Missal, ed. typ. tertia (reimpressio emendata), released in 2008. Celebrations that are added or changed are cited from official decrees.
Celebration names are used from English "Roman Missal" (2018).
Particular calendars.
The General Calendar is printed, for instance, in the Roman Missal and the Liturgy of the Hours. These are up to date when printed, but additional feasts may be added later. For that reason, if those celebrating the liturgy have not inserted into the books a note about the changes, they must consult the current annual publication, known as the "Ordo", for their country or religious congregation. 
These annual publications, like those that, disregarding the feasts that are obligatory in the actual church where the liturgy is celebrated, list only celebrations included in the General Calendar, are useful only for the current year, since they omit celebrations impeded because of falling on a Sunday or during periods such as Holy Week and the Octave of Easter.
This distinction is made in application of the decision of the Second Vatican Council: "Lest the feasts of the saints should take precedence over the feasts which commemorate the very mysteries of salvation, many of them should be left to be celebrated by a particular Church or nation or family of religious; only those should be extended to the universal Church which commemorate saints who are truly of universal importance."
Diocesan and parish calendars.
The calendar for a diocese is typically based on a national calendar, with a few additions. For instance, the anniversary of the dedication of the cathedral is celebrated as a solemnity in the cathedral church and as a feast in all the other churches of the diocese. The feast day of the principal patron saint of the diocese is celebrated as a feast throughout the diocese.