Some spoilers
Alright so after completing the first raid in Rabanastre; it is with absolute certainty that everything that took place within Ivalice happened thousand of years ago in FFXIV. Over the years people have forgotten and started thinking of Ivalice as a fairy tail. (that's about to change)
Final Fantasy XIV - Return to Ivalice - The Royal City of Rabanastre - Argath Thadalfus boss
https://www.youtube.com/watch?v=l8yhEo4cQNk