I set my G-Shock GA1000-A1 with the atomic clock at time.gov on the day I received it, and verified the accuracy today, 25 days later.  This watch is still to-the-second accurate with time.gov.  I am absolutely delighted with this watch, do recommend it and would buy it again.  Accurate, rugged, handsome, great power-lume, easy to read in all lighting conditions, strongly water-resistant... this is an outstanding watch.