© 2010, Father Kevin Michael Laughery, Holy Cross Parish, Diocese of Springfield in Illinois, USA, Roman Catholic Church
Last update and upload: Friday, February 19, 2010

PERPETUAL CALENDAR: The "Hard" (?) Way

The Easy (?) Way: The fourteen calendars necessary for a perpetual calendar. | Which of the fourteen calendars goes with which year | Back to Boring Stuff

PERPETUAL CALENDAR
translated and adapted from that appearing in the Calendario Atlante De Agostini, 1985

This "perpetual calendar" permits one to determine the day of the week corresponding to any date from the beginning of the common era to December 31, 2399. Establishing the date (for example, January 17, 1963), first of all find, in the column of the pertinent century (1900), the letter in the horizontal line with the last two digits of the year (63); in our case the letter is F. Then find in the table of months in what column the letter F appears in a horizontal line with the desired month (January): in our case, the sixth column. Finally in the corresponding vertical column (that is, the sixth) of the table of days, find the day of the week that appears in the horizontal line with the desired date (17): it turns out that January 17, 1963, is a Thursday.

For leap years there are two letters corresponding to the year. Use the first letter for January and February, and the second for the other months.

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CENTURY (Julian Calendar) from A.D. 1 to October 4, 1582

   0    100    200    300    400    500    600
 700    800    900   1000   1100   1200   1300
1400   1500

DOMINICAL LETTER                                YEAR (last two digits of the desired year)

DC     ED      FE    GF     AG     BA     CB    00
B      C       D     E      F      G      A     01   29   57   85
A      B       C     D      E      F      G     02   30   58   86
G      A       B     C      D      E      F     03   31   59   87
FE     GF      AG    BA     CB     DC     ED    04   32   60   88
D      E       F     G      A      B      C     05   33   61   89
C      D       E     F      G      A      B     06   34   62   90
B      C       D     E      F      G      A     07   35   63   91
AG     BA      CB    DC     ED     FE     GF    08   36   64   92
F      G       A     B      C      D      E     09   37   65   93
E      F       G     A      B      C      D     10   38   66   94
D      E       F     G      A      B      C     11   39   67   95
CB     DC      ED    FE     GF     AG     BA    12   40   68   96
A      B       C     D      E      F      G     13   41   69   97
G      A       B     C      D      E      F     14   42   70   98
F      G       A     B      C      D      E     15   43   71   99
ED     FE      GF    AG     BA     CB     DC    16   44   72
C      D       E     F      G      A      B     17   45   73
B      C       D     E      F      G      A     18   46   74
A      B       C     D      E      F      G     19   47   75
GF     AG      BA    CB     DC     ED     FE    20   48   76
E      F       G     A      B      C      D     21   49   77
D      E       F     G      A      B      C     22   50   78
C      D       E     F      G      A      B     23   51   79
BA     CB      DC    ED     FE     GF     AG    24   52   80
G      A       B     C      D      E      F     25   53   81
F      G       A     B      C      D      E     26   54   82
E      F       G     A      B      C      D     27   55   83
DC     ED      FE    GF     AG     BA     CB    28   56   84
====================================================================================================================================
CENTURY (Gregorian Calendar) from October 15, 1582 to December 31, 2399

1500   1600    1700  1800   1900
       2000    2100  2200   2300

DOMINICAL LETTER                   YEAR (last two digits of the desired year)

--     BA      C     E      G      00
F      G       B     D      F      01   29   57   85
E      F       A     C      E      02   30   58   86
D      E       G     B      D      03   31   59   87
CB     DC      FE    AG     CB     04   32   60   88
A      B       D     F      A      05   33   61   89
G      A       C     E      G      06   34   62   90
F      G       B     D      F      07   35   63   91
ED     FE      AG    CB     ED     08   36   64   92
C      D       F     A      C      09   37   65   93
B      C       E     G      B      10   38   66   94
A      B       D     F      A      11   39   67   95
GF     AG      CB    ED     GF     12   40   68   96
E      F       A     C      E      13   41   69   97
D      E       G     B      D      14   42   70   98
C      D       F     A      C      15   43   71   99
--     CB      ED    GF     BA     16   44   72
--     A       C     E      G      17   45   73
--     G       B     D      F      18   46   74
--     F       A     C      E      19   47   75
--     ED      GF    BA     DC     20   48   76
--     C       E     G      B      21   49   77
--     B       D     F      A      22   50   78
--     A       C     E      G      23   51   79
--     GF      BA    DC     FE     24   52   80
--     E       G     B      D      25   53   81
C      D       F     A      C      26   54   82
B      C       E     G      B      27   55   83
AG     BA      DC    FE     AG     28   56   84
====================================================================================================================================
MONTH                      DOMINICAL LETTER

January, October           A  B  C  D  E  F  G
February, March, November  D  E  F  G  A  B  C
April, July                G  A  B  C  D  E  F
May                        B  C  D  E  F  G  A
June                       E  F  G  A  B  C  D
August                     C  D  E  F  G  A  B
September, December        F  G  A  B  C  D  E

DATE                       DAY OF THE WEEK

1    8   15   22   29      Su Sa Fr Th We Tu Mo
2    9   16   23   30      Mo Su Sa Fr Th We Tu
3   10   17   24   31      Tu Mo Su Sa Fr Th We
4   11   18   25           We Tu Mo Su Sa Fr Th
5   12   19   26           Th We Tu Mo Su Sa Fr
6   13   20   27           Fr Th We Tu Mo Su Sa
7   14   21   28           Sa Fr Th We Tu Mo Su
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