to_date & to_char with postgres 6.5 & 7.0

 I have a database in production under 6.5 and i need to use the to_date and
to_char function.
I planned to migrate to postgres 7.0 later but i need a compatibility from now
for my projects.

Where do i find the postgres65.sql to install this functions under postgres 65 ?

thanks,
oliver