WEEKDAY
Determine the Day of the Week
WEEKDAY
is a FORTRAN77 library which
can determine the day of the week corresponding to a given date;
for instance, the battle of Hastings, on 14 October 1066 (Julian Calendar!),
was a Saturday.
Licensing:
The computer code and data files described and made available on this web page
are distributed under
the GNU LGPL license.
Languages:
WEEKDAY is available in
a C version and
a C++ version and
a FORTRAN77 version and
a FORTRAN90 version and
a MATLAB version.
Related Data and Programs:
ANALEMMA,
a FORTRAN77 program which
evaluates the equation of time, a formula for the difference between
the uniform 24 hour day and the actual position of the sun,
creating data that can be plotted by gnuplot,
based on a C program by Brian Tung.
CALENDAR_NYT,
a FORTRAN90 library which
shows the correspondence between dates and the New York Times volume and
issue number;
CALENDAR_RD,
a C++ program which
computes the representation of a given date in a
number of calendrical systems,
by Edward Reingold, Nachum Dershowitz
CALPAK,
a FORTRAN90 library which
makes various calendar calculations;
DATES,
a dataset directory which
contains lists of dates in various calendar systems.
DOOMSDAY,
a FORTRAN77 library which
is given the year, month and day of a date, and uses
John Conway's doomsday algorithm to determine the corresponding day of the week.
TEST_VALUES,
a FORTRAN77 library which
supplies test values of various mathematical functions.
Reference:

Lewis Carroll (Charles Dodgson),
To Find the Day of the Week for Any Given Date,
Nature, 31 March 1887.

Gary Meisters,
Lewis Carroll's DayoftheWeek Algorithm,
Math Horizons,
November 2002, pages 2425.

Edward Reingold, Nachum Dershowitz,
Calendrical Calculations: The Millennium Edition,
Cambridge University Press, 2001,
ISBN: 0521777526,
LC: CE12.R45.

Edward Richards,
Mapping Time, The Calendar and Its History,
Oxford, 1999,
ISBN: 0198504136,
LC: CE11.R5.
Source Code:
Examples and Tests:
List of Routines:

DIGIT_TO_CH returns the character representation of a decimal digit.

I4_MODP returns the positive remainder when I is divided by J.

I4_TO_S_LEFT converts an integer to a leftjustified string.

I4_TO_S_ZERO converts an integer to a string, with zero padding.

I4_WRAP forces an integer to lie between given limits by wrapping.

JED_TO_WEEKDAY computes the day of the week from a JED.

S_CAT concatenates two strings to make a third string.

TIMESTAMP prints the current YMDHMS date as a time stamp.

WEEKDAY_TO_NAME_COMMON returns the name of a Common weekday.

WEEKDAY_VALUES returns the day of the week for various dates.

Y_COMMON_TO_ASTRONOMICAL converts a Common year to an Astronomical year.

YMD_TO_S_COMMON writes a Common YMD date into a string.

YMD_TO_WEEKDAY_COMMON returns the weekday of a Common YMD date.

YMDF_COMPARE compares two YMDF dates.

YMDF_TO_JED_COMMON converts a Common YMDF date to a JED.

YMDF_TO_JED_GREGORIAN converts a Gregorian YMDF date to a JED.

YMDF_TO_JED_JULIAN converts a Julian YMDF date to a JED.
You can go up one level to
the FORTRAN77 source codes.
Last revised on 26 May 2012.