Converting lat/lng to GMT offset

gistfile1.rb

class TimeZoneFinder
  def self.find_gmt_offset(lat,lng)
    uri = URI.parse("http://ws.geonames.org/timezone?lat=#{lat}&lng=#{lng}")
    doc = Hpricot.XML(Net::HTTP.get(uri))
    (doc/"geonames"/"timezone"/"gmtOffset").innerHTML.to_f
  end
end

offset = TimeZoneFinder.find_gmt_offset(some_lat, some_lng)
timezone = ActiveSupport::TimeZone[offset]