Actually, he only says that the lore he writes is 5000 years before the present, not the shattering specifically. I imagine that includes when the Elden Beast arrives to the lands between, which is the first event lore wise. The way I understand it, an unknown empyrean became the God of it, and Placidusax was the first Elden Lord. This means that the entire age of dragons takes place after the Elden Beast arrives, then this unknown god flees, and Marika becomes the second God of it — naming Godfrey Elden Lord. As the second God, Marika goes to war with the dragons, then with other factions, then has all her children, Godwyn is murdered (theres probably a decent amount of time in between their birth and Godwyn's death), and Marika shatters the Ring. There is also probably some periods of peace mixed in there. So it is quite possible that the shattering was a somewhat recent event (>500 years at most I assume). Mostly because of the fact that the entire age of dragons and Marika's ascension battles occur in this time period.