WEEKDAY.COM - A Julian date calculation program by Kevin Smith.

    The Julian day number as well as the day of the week are calculated
for any date.  The menu driven program also has options for determining
the number of days between two dates (ever wonder how many days old you
were?),  as well as the number of days between a date and the beginning
of that year.

    Years are entered by putting the month number first (i.e., 7 = July),
followed by any delimiter (other than a number, plus or minus sign), the
day number of that month, a delimiter, and finally the entire year number.
Examples - April 6, 1985 could be entered as 4/6/1985 or even  4 6 1985.
         - Jan. 1, B.C. 7 as 1/1/-7
         - Jan. 1, A.D. 7 as 1/1/7 or 1/1/+7

    Upon entering a date value (in the program), the date is always check-
ed for validity.  If an invalid date is entered, the date prompt will re-
appear, and this will continue until a valid date is finally entered.
Obviously a month value greater than 12 or less than 1 is invalid.  As well
as day values greater than 31 or less than 1.  Further if the month is one
that only has 30 days, then putting 31 is invalid; the same applies for
February with the value of 28, except for the fact that if the year entered
was a leap year, then a day value of 29 is accepted.  The year value can
be any value except 0 (the year before 1 A.D. was 1 B.C.) [Since the year
is represented as a two-byte integer, the year values should be kept within
plus or minus 32000].

    Since WEEKDAY.COM is menu driven, there is little need to explain the
operation of the program, just give it a try.

    While the program will calculate the desired information for ANY date,
it should be kept in mind that due to the readjustments that took place in
the Julian calendar, very old dates are not guaranteed to be correct.  I
have tried a couple of dates that were over 1500 years ago that all resolved
to the correct values, but this in no way is meant to imply that all dates
back that far will evaluate correctly.

    No run time options are required in running WEEKDAY.COM, and in fact any
run time options included will be ignored.  The source should be found
included in the .LBR.  The program was written using  the CP/M version of
TURBO Pascal Ver. 3.0.  It has been compiled using the General Installation
program offered by Borland International, so to run the program on another
CP/M machine with an incompatible screen, running WDAYINST.COM will allow
you to customize the object code to your computer (without re-compiling, in
fact, having TURBO Pascal is unnecessary).  Documentation on running WDAYINST
is found in WDAYINST.DOC (but the file will probably have to be printed
rather than displayed).

    A machine running PC-DOC or MS-DOS can, of course, re-compile the source,
assuming that the owner of the machine has TURBO.  But since I used two CP/M
dependant standard function calls (v.z., Ptr & Addr), the source will have
to be changed in the couple of places that they are used.