Chronology (from Latin chronologia, from Ancient Greek χρόνος, chronos, "time"; and -λογία, -logia) is the science of arranging events in their order of occurrence in time. Consider, for example, the use of a timeline or sequence of events. It is also "the determination of the actual temporal sequence of past events". 

A simple timeline. image: R.Conan-Davies

Chronology is part of periodization. It is also part of the discipline of history, including earth history, the earth sciences, and study of the geologic time scale