InterCal is a very simple freeware calendar comparison and holiday calculation program. It is not a daily appointment calendar. It displays calendars, one month at a time, for any month of any year in any of several calendar systems. For each day in the displayed month, corresponding dates in another calendar system can be shown. For any selected single day, the corresponding dates in all implemented calendar systems can appear in a separate window.
Calendar systems implemented are: Julian, Gregorian, "Western Historical" (a cross between the Julian and Gregorian), Jewish, Islamic, and the Elliott Super (invented by the author of InterCal).
Certain religious holydays and festivals are highlighted (under user control) when they occur in a displayed month, regardless of which calendrical system is in use at the time. Some which can be highlighted are Easter, Rosh Hashonah, Hanukah, ‘Id al-Fitr, and the first day of Ramadan.
Limitations
InterCal was designed with 16-inch or larger monitors in mind. But smaller monitors can be used if one is willing to scroll around the display. InterCal exists in a 680x0 version only (no native Power PC version).
InterCal requires System 6 or later (it uses pop up menus) and 32-bit QuickDraw. Actually, it will run without 32-bit QuickDraw with some annoying but non-fatal display anomalies.
InterCal was developed and tested on a Mac IIci running System 7.1. It has been run and casually tested on several other machines (MacPlus, PowerBook, Centris, Performa, PowerMac) running System 6.0.5, System 7.0.1, System 7.1, and System 7.1.2.
Acknowledgements
InterCal was developed using Symantec's C++ Version 7.0, Symantec's Visual Architect™, and the Think Class Library. Using those tools shortened development time considerably, but lead to an unexpectedly large size for such a simple program. It requires 640K to run.
The InterCal icon was designed and drawn by my 13-year-old daughter Nicole.
As described in more detail in "Calendar System Facts", my ability to include the Jewish calendar depended on access to the source code to a freeware program called "Jewish Calendar" written by Frank Yellin.
Package Contents (A folder containing seven items)
(1)—This ReadMe file, which was written using SimpleText, not TeachText, and so has some text styling which will not be visible if viewed using TeachText;
(2 and 3)—A User's Guide (included for completeness—InterCal is a simple program with very few commands and should be easy to figure out without a manual)—distributed as both a SimpleText document (for general readability) and as a Word™ document (for better formatting and graphics);
(4, 5, and 6)—A document entitled "Calendar System Facts" which contains a general discussion of calendars and descriptions of each implemented calendar—also in SimpleText and Word™ format. The SimpleText document had to be split into two parts because SimpleText is limited to rather short documents.
No one may distribute InterCal for profit in any form, including (but not limited to) electronic information service distribution, bulletin board distribution, and magnetic or optical medium distribution. Non-profit distribution of the software is fine, providing that the software is not modified in any way, and the complete works and documentation of the software are included in the distribution package.
Disclaimer
The formulas used in the various calendars and the statements concerning calendars made in "Calendar System Facts" are true to the best of my knowledge. However, their accuracy is not guaranteed.
Comments, corrections, bug reports, and suggestions are welcome via e-mail to the following Internet address:
