The Paris Observatory has announced that it will add one ‘leap’ second to clocks this summer. This is in addition to the leap year on which an extra day is added to the calendar every fourth year. (Source).
This is being done so Earth’s rotation can catch up with atomic clocks that are believed to be constant. Notice I stated ‘believed’ to be constant. It isn’t.
Time is defined as the period of revolutions the Earth makes around the sun along its orbit, from say winter solstice to the next winter solstice. The second is simply a fraction of that period and these days strictly defined by the atomic frequency of the Cesium atom.
The current time standard for the United States is a cesium atomic frequency standard at the National Institute of Standards and Technology in Boulder, Colorado. In 1967 a standard second was adopted based on the frequency of a transition in the Cs-133 atom:
1 second = 9,192, 631,770 cycles of the standard Cs-133 transition
What is a cycle? It is a synonym for frequency, so 1 second is = 9,192,631,770 cycles becomes:
S = 9,192,631,770 Hz. = 9,192,631,770 W/S where W = wavelength and S = second. How do you measure frequency? With an instrument of course but calibrated on what standard?
It is described in the hi-falutin description above to avoid one coming to the realisation that it is a circular argument in that the second is defined in terms of itself, so it is blindingly obvious that it is absolutely accurate, except that it does not relate to physical reality.
If leap years are needed and leap seconds as well, then time itself, as defined by the second, is not constant. Ordinarily this fact does not have any direct effect on calculating the motion of objects using Newton’s laws, since the discrepancy in time versus the practical distance travelled can be ignored.
However it is clear that as the Earth is slowing down, and is it slowing down around its diurnal rotation, or along its orbit, then time itself is not constant and hence the plotting of measurements versus a time axis for geological and astronomical measurements becomes problematical, especially if the present definition of the second is based on the Gregorian Calendar implemented during 1582 CE.
Astronomical retrocalculation, as well as and time based series using the present day value of time is thus limited to when the present day Earth-Sun configuration was attained.
And because the Julian Calendar, first implemented 47 BC (?), ended up being out by some 11 days after 235=935 CE (Heinsohn thesis) then one presumes that a significant change in solar geometry occurred at 935CE making the Julian Calendar redundant, and necessitating the Gregorian Calendar.
And as the Earth is still slowing down, (around its axis or orbit), then time is not a constant.
This has serious implications for forecasts based on time series, whether forward or backward.
I hasten to add that only creationists, who have to have a T=0 axiom, will be upset with this implication. So too will their brethren among the secular humanists who believe in The Big Bang and evolution.
Update: Radiometric dating assumes radioactive decay is statistically constant, along with time also being a constant. But neither are constant.