From: "Martin J. Laubach" <mjl@CSlab.tuwien.ac.at>

Subject: [PATCHES] libpq SET var TO patch

  One last, I hope. This one corrects a bogus format string, and
actually sends the contents of PG_DATESTYLE to the backend. That
means, you can do a setenv PG_DATESTYLE 'iso', and your libpq
will pick that up and tell the backend.