Define relative dating science
Paleontologists have examined layered sequences of fossil-bearing rocks all over the world, and noted where in those sequences certain fossils appear and disappear.
When you find the same fossils in rocks far away, you know that the sediments those rocks must have been laid down at the same time.
In fact, I have sitting in front of me on my desk a two-volume work on is not light reading, but I think that every Earth or space scientist should have a copy in his or her library -- and make that the latest edition.
In the time since the previous geologic time scale was published in 2004, most of the boundaries between Earth's various geologic ages have shifted by a million years or so, and one of them (the Carnian-Norian boundary within the late Triassic epoch) has shifted by 12 million years.
This is called the chronostratigraphic time scale -- that is, the division of time (the "chrono-" part) according to the relative position in the rock record (that's "stratigraphy").
Venus, Io, Europa, Titan, and Triton have a similar problem.
On almost all the other solid-surfaced planets in the solar system, impact craters are everywhere. We use craters to establish relative age dates in two ways.
With this kind of uncertainty, Felix Gradstein, editor of the For clarity and precision in international communication, the rock record of Earth's history is subdivided into a "chronostratigraphic" scale of standardized global stratigraphic units, such as "Devonian", "Miocene", " ammonite zone", or "polarity Chron C25r".
Unlike the continuous ticking clock of the "chronometric" scale (measured in years before the year AD 2000), the chronostratigraphic scale is based on relative time units in which global reference points at boundary stratotypes define the limits of the main formalized units, such as "Permian".