(01-14-2014, 02:22 AM)Tiergan Wrote: Eras are not a measurement of time. Astral and Umbral Eras are just names used to denote periods of abundance/disaster.
http://ffxiv.gamerescape.com/wiki/Time
They're marked by years though. 1500 years is not the amount of years ever. 1572 is the amount of years since the start of the 6th Astral Era, which came after the 5th Umbral which was a calamity.
"Eras" can be equated to "Dynasties" more or less. They're a subsection of the time spectrum that may overlap with another societies way of grouping time.