HP 9000 User Manual page 44

Note
If you find that date works according to the current setting of
LANG,
but
cat
does not, this means a message catalog for
cat
has not been installed on your system for the selected language.
The date command relies on language tables and library
routines, rather than message catalogs, so not having a message
catalog installed for the selected language does not affect it.
Using International Software 3-7
3