Year benchmarks

Cris-

Why don't you research "calendars" on wikipedia?

Go here.

Major historical events. Conquests, dynasties, the births and deaths of nations. Note that even trying to define a 'year one' gets into murky territory, since there probably aren't any records that go back that far (or if there are, they probably aren't commonly known). You may be getting into year-count-defined-by-religion at that point anyway, because what was before year one? How do these people know? Would someone who was there and is around to tell about it be considered a god?

Also, time may not have functioned quite the same way in Universal Year One as it does now.

If your story involves humans, then my suggestion would be to create a calendar much in the way that humans have. The wikipedia article Ted cited is a great place to start.

The elves of Middle earth used "ages" to indicate major epochs. The events surrounding Frodo and the Fellowship of the Nine that took place during the War of the Ring, as depicted in the film The Lord of the Rings took place at the end of the Third Age.

At the same time, the hobbits of the Shire marked their years in 'Shire Reckoning' years, which is to say, the founding of the shire.

That would be akin to calling today "June 25, 233-American"

In one of my WIPs, I have five calendars currently in use. All use basically the same day/week/month structure based on the passage of the twin moons, but the baseline for Years is wildly different.

One starts at a great natural disaster
One starts with the founding of an empire (destroyed by the disaster)
One start with the founding of a confederation of city-states
One is the demonic calendar used by worshipers in various kingdoms.
One starts over again with every new dynasty in their kingdom.

The calendar the readers will be the most familiar with is the third one (where I mention months and years), but as the characters discover artifacts, ancient coins or other clues, they may be set in the other systems to add some mystery.

(Not horribly different than the Western/Jewish/Arabic/Japanese/Chinese calendars we currently use.)

I've toyed with using concurrent calendars for different factions/power centers. One uses the coronation of the current king and the start of his dynasty as moving reference points with each dynasty (there have been several), the other uses a single point of the completion of a book that they revere.

Other milestones have been mentioned - founding/collapse of an empire, religious figure, disasters, discovery of a new land. These all can work well.