Dominical Letter
         In order to understand Dominical Letters, it is helpful to be aware of some traditions inherited from the ancient Roman calendar.
         Like our own, early Rome's major calendar division was into months, each of which was listed in a separate vertical column on their marble and painted calendars (a three-month portion of one is shown to the right). On the far left side of each month's column they indicated days of their Nundinae, an 8-day week, using a continuously recurring cycle of the letters A through H. This cycle began anew with an A for the first day of every year.
         Months were also divided into three sections named Kalends, Nones and Ides. In the first line of every month the second letter is a lower case k, an abbreviation for Kalends. From four to six days down in each month's columns are the letters "NON," which indicate Nones. Then, eight days lower are letters "EIDVS," signifying the last day of the Ides section.
         At the time of Rome's second king Numa, the 23rd day of February was the last day in Rome's calendar year. It is shown in the February column as "TERMI," which also indicates that the day honors Terminus, their god of boundaries.
         When adjustments were made to the Roman calendar (as needed to return named days to their former season) additional days or months always followed the February 23rd feast day of Terminalia. Because the following day during the Julian Calendar's time was known as the sixth of the Calends of March, and subsequent days (up until Pridie) were the fifth through second of that segment, in intercalary years the additional day in February was also known as the sixth of the Calends of March.
         Doubling up of that day during intercalary years, as well as some of the other traditions mentioned here, were adopted by the Catholic church when it first made use of the old Roman calendar. These traditions have been continued up to the present time.
   Januarius thru Martius.
         Every year, letters from A through G are used to name days of the week in Catholic ecclesiastical calendars, just as A through H were used in the ancient Roman calendar. They are also given to each day in alpha sequence, starting with January 1. Each day in every week of the year can then be identified by one of these seven letters, rather than using one of the heathen-inspired names of Monday thru Sunday. The letter that happens to relate to Sunday in other Gregorian calendars is known in church circles as that year's Dominical Letter.
         An exception is during intercalary years, in which the letter for the day after the 23rd of February is repeated the following day, so like in the old Roman times that calendar day occurs twice in succession. As a result, all of the letters then "leap" back for the remainder of the year and occupy one position prior to where they had been (relative to days of the week) thru the first 23 days of February. Hence the term "leap year."
         For example, New Year's Day of the intercalary year 2000 will be a Saturday, so that year's Dominical Letter is a B for all Sundays thru the Wednesday of February 23, which is an E. The letter for the two days following that Wednesday will each be an F. So when Sunday the 27 rolls around, its Dominical Letter will be A, as will that of all Sundays for the remainder of 2000.
         So what secular calendars will show as February 27, a Sunday, and all following Sundays of 2000, will have the Dominical Letter of A. That year, therefore, will be blessed with not one but two Dominical Letters—B and A, in that order.
         Catholic Encyclopedia: DOMINICAL LETTER has a formula for calculating the Dominical Letter for any year. As would be expected, using that formula for the centurial year 2000 provides the number 6, which (according to the page's instructions) confirms that 2000's second Dominical Letter will be an A.

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Last revision:  February 22, 1998
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