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On earth, your reference frame is essentially fixed with respect to everything else on earth. At which point the rate of progression of time is constant.Certainly our units of time are arbitrary based on earth's rotational period, and earth's orbital period.
The second as the basic unit measure of time, which not very long ago was determined with reference to the rotation of our planet, it is nowadays officially defined as: «the time required for the speed of light to travel a distance of 299.793 kilometres in vacuum». We have to leave it at that, thank you.
The metre is the length of the path traveled by light in vacuum during a time interval of 1/299,792,458 of a second.
"The second is the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom."13th CGPM (1967/68, Resolution 1; CR, 103)"This definition refers to a caesium atom at rest at a temperature of 0 K."(Added by CIPM in 1997)