Day of week vs. Language

Hello together,

the documentation of PGSQL 8.0 tells me, that extract(dow ...) will
return 0 for Sundays. I know that this behaviour depends on the
language settings on MSSQL, so that I have to correct this settings
with an offset. What is the behaviour in PGSQL? Does the dow result
also depend on the language settings, or will the value 0 ALWAYS be a
Sunday?

Thanks in advance,
Stefan