DDEMO.TXT (a description of Julian/Gregorian date functions and modifications)

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DateDemo and it's derivatives, DDemo1,2 & 3 are based on a modified Julian
calendar which starts at 01-01-1900 vs. the original Julian calendar which
began somewhere around 46 B.C., although it's actual start date is unknown to
me. Other sample Julian source code I've looked at indicates a start date of
11-25- -4713. Historical accuracy aside, for most instances the modified
version should suffice quite nicely.

What is most useful about the Julian calendar is the ability to determine dates
as a number of days into the future or into the past from some reference date.
It is also an expedient way to determine the differences in days between dates
and the relationship of one to the other. We currently use (and are familiar
with) the Gregorian calendar. The Julian calendar assigns a value which is the
number of days elapsed since that start date of the calendar. Comparing dates
or determining a date in the future (or past) from some reference date is as
simple as adding, subtracting or comparing two numbers.

Although the start date of the modified Julian code (DateDemo.Bas and it's
derivatives) is 01-01-1900, dates prior to this date can be used and will be
represented by a negative number. DateDemo is the original source as I found it
and is limited to a date range of 1900 to 1999. DDemo1 was slightly altered to
run in Qbasic or Quick Basic as well as GW Basic and is functionally the same as
the original DateDemo.Bas. DDemo2 was modified to include dates prior to 1900
and beyond 1999 and will run in GW Basic, QBasic or Quick Basic. DDemo3
structures the conversion code as function calls which simplifies usage but is
restricted to QBasic or Quick Basic only. The structure could be converted to
GW Basic subroutines for incorporation into other programs if desired.

DateDemo and DDemo1 continuously generate pseudo random numbers for the month,
day and year and are displayed in the differing formats in addition to Day of
the Year and Day of the Week. These programs will run until you "Control Break"
to stop. DDemo2 and DDemo3 will display the current date as a function of the
internal DOS clock/calendar and stop. DDemo3 has been compiled (DDEMO3.EXE) in
case you just want to see what the program does without using Basic.

In the true spirit of computing I would like to thank and commend
Richard L Tremmel for generating the original source code and making it
publicly available with no strings attached. This has allowed me to make the
minor modifications necessary for use in the versions of Basic that have become
popular since this programs inception and in that spirit I pass the program to
you. Accuracy and suitability to task is subject to your determination.

                             Best Regards;

                                       Robert Lund



         
         From Websters Unabridged Dictionary;

         Julian calendar: the calendar introduced by Julius
         Caesar in 46 B.C., in which the ordinary year had
         365 days with every fourth year given 366.
         The months were the same as in the Gregorian, or
         New Style, calendar now used.
         
         Gregorian calendar: a corrected form of the Julian
         calendar, introduced by Pope Gregory XIII in 1582
         and now used in most countries of the world: it
         provides for an ordinary year of 365 days and a
         leap year of 366 days every fourth, even year,
         exclusive of the final year of a century, which is
         a leap year only if exactly divisible by 400