request!

Hello everyone, I am Peter Smit and working for Gatsometer Holland in R&D. Our equipment for traffic control is exported all over the world. I am looking for some data base or algorithm that produces GMT offset or TZ name if longitude and latitude are input from GPS. Perhaps you know someone or an institute that can help. I have already take a look at ftp://elsie.nci.nih.gov/pub/tzdata*.tar.gz and found there the file zone.tab. Thanks for your response. Regards, Peter Smit