Coordinated Universal Time (UTC) is based on International Atomic Time (TAI), but it is adjusted by leap seconds to account for the difference between the definition of the second and the rotation of Earth. This correction keeps UTC in conjunction with the apparent position of the Sun and the stars, and it is the standard used for all general timekeeping applications.
The first leap second was inserted into the UTC time scale on June 30, 1972. Leap seconds are used to keep the difference between UT1 and UTC to within ±0.9 s.
NOTE: 1972-1982 11 leap seconds were added in 10 years.
1998-2015 5 leap seconds were added in 18 years.
Leap Seconds are now being added less frequently. This does show that the earth is rotating faster. This means the inertia of earth has decreased due the massive snows that we have had during the past decade. More snow has moved water from the low latitude oceans to ice on high latitude land. This means that the ice volume at and near the poles and northern latitudes has increased and that means that ice will advance and albedo will increase and it means the oceans are dropping and not rising. The warming cycle of the past three hundred years is likely over, or nearly over and we are in a warm phase, like the Roman and Medieval Warm periods. It will stay warm and snow more for the next several hundred years. Then the ice will advance and we will be in the cooling phase toward a next little ice age. Some of the glaciers are still retreating because it is still warm, but, overall, they are being replenished at their source at a faster rate. Greenland and the Antarctic Continent and ice packs and glaciers are being replenished on top at a faster rate than they are losing from the sides and bottoms. The leap seconds changes and earth rotation rate increase does show that.
Tom Wysmuller presented the leap second data in a presentation at a Climate Symposium that was sponsored by the JSC NASA Alumni League at NASA JSC Gilruth center In September 2011. Since then I have included it in my presentation.