## Dynamic Time

Universal Time (UT) or Greenwich Civil Time, used in civilian life, is based on the rotation of the Earth. However, this rotation slows down unpredictably, so UT is not a uniform time. Astronomers, in need of uniform time, utilize Dynamic Time noted TD and defined by atomic clocks. The difference ΔT=TD - UT can only be deduced from observation.

### Here are some value of the difference ΔT = Dynamic Time - Universal Time observed betwwen 1600 and 2000:

### From 2000 to 2100 the difference ΔT = Dynamic Time - Universal Time can be aporiximated with:

With t = (year - 2000) / 100

ΔT= 102 + 102 * t + 25.3 * t

ΔT= 102 + 102 * t + 25.3 * t

^{2}+ 0.37 * (year - 2100)