Even better, GPS itself is sending out the exact UTC offset (and start of validity/moment of insertion of leap seconds)... http://www.losangeles.af.mil/shared/

Even better, GPS itself is sending out the exact UTC offset (and start of validity/moment of insertion of leap seconds)... http://www.losangeles.af.mil/shared/media/document/AFD-100813-045.pdf http://www.losangeles.af.mil/shared/media/document/AFD-10081... §20.3.3.5.2.4