The Tcal program runs the Gcal program with the date of tomorrow's day1. Its arguments are as follows:
tcal [--help | --version] | [--shift=[+|-]number] [argument...]
All given arguments are passed unmodified to the Gcal program. If the Gcal program shall be called with another date than tomorrow's date, this desired date can be selected by using the --shift=[+|-]number option, in which [+|-]number is the distance of days the desired date is distant from the actual system date (==today). (Works only for Gregorian years.) The --shift option must be given before all other arguments that are passed to the Gcal program.
In case a GCALPROG environment variable
(see Environment Variable GCALPROG)
is defined and set with the file name of the executable Gcal program,
Tcal will use this file name for calling Gcal. Otherwise, the file name
gcal —which is burned-in during the compilation step of the
Tcal program— is used for calling the Gcal program. The GCALPROG
environment variable must always be set if the Gcal program is installed
under another name than the standard name gcal, otherwise Tcal
is unable to execute the Gcal program automatically! An exit status
of 0 means all processing is successfully done, any other value means
an error has occurred.
The program accepts the following options:
 This is equivalent the --shift=1 option.