Every year that's happened before the present has passed similar to our own, most visibly with regards to Minfillia, who was a child ten years before 1.0 and then an adult by the time of 1.0 proper. It's pure out-of-story fiat that the events in FFXIV are conveniently not explicitly marking off time within the story. There's no need to think up convoluted reasons why 1577 has lasted so long, besides the writers not wanting to commit to moving onto 1578.
EDIT: It's left entirely up to us as players to decide on what would be a more realistic timeline for ourselves, because it's a headache that the writers are basically saying they're not interested in wrangling.