libpg date/timestamps format used by PQgetvalue

Hello everyone,

I've been unsuccessful in finding the place in the documentation which
describes how to determine the format of dates and timestamps in the
string returned by PQgetvalue.  It's been reported that on some systems
we get something like:

%d/%m/%Y %H:%M:%S.00 %Z

and others:

%m-%d-%Y %H:%M:%S %Z

Is this version/local dependent?  Or better yet, is there an API in
which we can query about the format or even set it?

I'd like to avoid wrapping all date and timestamp attributes in
to_char() if possible.

Thanks for any advice or pointers.

Cheers,
David

PS: I'm not subscribed.