Here’s a helpful categorization I found in reading Ancient Near East: Historical sources in translation by Chavalas, et al this morning (what follows is a quotation):

In the ancient Near East three different methods were used (at different times and in different places) to distinguish years:

1. Years were named after an important event (year names)

2. The years of a king’s reign were numbered consecutively (regnal years)

3. Each year was named after a high official called a limmu (eponym)