GPS time#Timekeeping

GPS time is the time system of navigation satellites of the Global Positioning System ( GPS). It corresponds to - up to a constant of 19 seconds - the International Atomic Time ( TAI ). Compared to the Coordinated Universal Time (UTC) it deviates currently (since 1 July 2012) was 16.0 seconds; this value is in the future with each leap second - the average so far had to be added every 2 years - increase by 1 second.

The GPS time scale starting on January 5, 1980 at 24:00:00 (see also GPS week ) and was then identical to the UTC. This in turn had at this time a difference to TAI by 19 seconds. Since then, all 1-6 years had to be inserted leap seconds to keep the world time with the earth's rotation in sufficient accord with what is not taken into account in GPS. The GPS time is thus the same as the UTC to this difference ( integer seconds).

As part of the transmitted payload with GPS, the current difference between the GPS time and UTC is transmitted in a separate data field. GPS receivers can automatically display by subtracting the appropriate number of leap seconds UTC time.

In numbers:

• January 6, 1980: GPS = UTC (or GPS = TAI - 19 s )
• 1981-1998: GPS = UTC 1 s to 12 s ( leap second every 1-2 years)
• From 1 January 1999: GPS = UTC 13 s
• From 1 January 2006: GPS = UTC 14 s
• From 1 January 2009: GPS = UTC 15 s
• From 1 July 2012: GPS = UTC 16 s ( and continues to GPS = TAI - 19 s ).