G.2.2.2 Textual date %n[argument] special text

%n[[+|-]n] references the current respectively queried day number relative to the current date ‘+/-’ n days and is replaced by a date text by using the fixed ‘%>02*D-%>3#U-%>04*Y’ format, e.g.:

The resource file line ‘1962Sep21 10000 days old: %n+10000’ will be expanded to
→ ‘10000 days old: 06-Feb-1990’, in case you call Gcal with the simple -c option and the command sep 1962 (see Single command mm yyyy).