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National Geodetic Survey

Explore: GPS

September 14 Marked One Billion Seconds of GPS Time

September 15, 2011
Person using GPS

Global positioning is fundamental to navigation, communication systems, mapping and charting, and much more. Here, a user employs a GPS receiver to instantaneously display present coordinates.

When the atomic clocks in GPS ground-control stations and GPS satellites around the world stuck 1:46 a.m. Greenwich Mean Time (GMT) on September 14, 2011, they marked a milestone for NOAA and, indeed, the entire planet: One billion seconds of GPS time had gone by.

Global Positioning System or GPS Time is derived from the atomic timescale implemented by the atomic clocks in those stations and satellites. The U.S. Department of Defense set the clocks to start GPS time at “zero” at 0-hour GMT on January 6, 1980. NOAA is proud to be a recognized leader in global positioning and navigation, as it has been for more than three decades, better known (at least at NOAA) as one billion GPS seconds!