How does geological time help scientists keep track of events in Earth’s history?

The geologic time scale (GTS) is a system of chronological dating that relates geological strata (stratigraphy) to time. It is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth's history.
en.wikipedia.org/wiki/Geologic_time_scale

Stratigraphy is not a reliable method. It is regarded as a "scientific wild guess".