Interesting page. Okay so just as a starting point, it's year 1378 in game, it's 2021 out here, game speed is 25x normal speed (please correct me if I'm wrong)
https://www.wolframalpha.com/input/?i=1378+%2B+25x+%3D+2021+%2B+x
26 years from now and change. Ignoring leap years, ignoring the fact that it's August in game vs June irl. So if someone more math savvy can nail down the exact date in 2047 that'd be terrific. I'll be turning 60 that year, and I'm optimistic those who are already 60 will make it.
-----Random observations while we're at it-----
According to some page I just found,
https://ffxiclopedia.fandom.com/wiki/Vana%27diel_Timeline
FFXI "started" in the year 884. Not at all sure if that was true, but if so, ~494 in-game years have passed. 494 / 25 = 19 real years and change, but it's like 19.75, which doesn't line up with the 19th anniversary unless some big in-game change caused the years to be thrown off from the real timeline (world merges? rollbacks?). Maybe it started later than 884. Does anyone actually remember or know of documentation? Would an old strategy guide have some flavor text mentioning something like "it was the year ____ and the three kingdoms such and such..."
881 is the newest year of Rolanberry item, which are supposedly "preserved", so at launch an item preserved for ~a couple decades at most checks out as reasonable.
https://www.ffxiah.com/item/4529/rolanberry-881