InterCal is a date conversion program and perpetual calendar. It is not a personal appointment calendar.
The program displays calendars, one month at a time, for any month of any year in any of nine implemented calendar systems. For each day, the corresponding date in any other system can be shown˜thus an entire month is converted at once.
Any single day can be selected and its equivalent listed in all systems.Certain Christian, Jewish, and Islamic holydays can be highlighted if the user wishes.
The implemented systems are: Gregorian, Julian, Western Historical (hybrid Gregorian/Julian), Jewish, Islamic, Chinese, Mayan, French Revolutionary, Persian, Afghan, Elliot Super.