A Timeline of the Ys Series

Because the Ys games are not released in chronological order (per Falcom's explanation, we are playing through the games in the order Adol's memoirs are being discovered), we can place each game on a timeline according to how old Adol was at the time of the game's events.

As cited in the Ys Wiki:

• BC stands for Before Christin.

The only game currently set before Adol's birth is Ys Origin.

• AC stands for, simply, After Christin('s birth).

A game's canonical "year" is equivalent to how old Adol was when it took place. So even though Ys I & II and Ys X were released more than 30 years apart, they still technically take place during the same year of Adol's life: 17 AC.

For fans of the series, this perhaps makes sense. After all, we already have direct equivalents to things in our own world with Ys's Afroca, the Romun Empire, Ispani, etc. Why not a BCE/CE-adjacent calendar system, too?

We also know from the original Ys I PC-88 Manual (translated) that Adol lives to be 63 years old, so we still have quite a large gap to fill in from Adol's exploring years.

If you'd like to know impossibly more information about the BC timeline, see Kirsten Miller's excellent (and spoiler-heavy, so be warned) article from 2016.