Eh, the DV isn't the real world, so it doesn't bother me when he uses examples that are common cultural touchpoints. Everyone knows about The Burning of the Library of Alexandria, after all, so it's not like Jim would bother to fact check something like that. And even if he did, reports about what happened are certainly not definitive; we don't know how much was lost when Caesar's fire spread (tens of thousands, but the Library could have held upward of half a million scrolls).
Like I said, we don't know that it was even still in operation when that area of Alexandria was destroyed around 270something AD—we just know that Roman scholars had stopped writing about it by then.
During Julius's time, that Library was one of the most well-respected places for scholarship (not really a college, but I don't know what else to call it). It'd be like burning down Harvard, or Cambridge, or Oxford. Only what's lost in the Library fire is quite literally irreplaceable.
I guess it'd be closer to, say, the Internet losing 5-25% of all of its unique information over the course of a couple of days (talking about stuff with no backups or hard copies, not just Wikipedia losing databases).
Anyway, over the following couple of centuries after Caesar's fire, Roman scholarship started focusing elsewhere. Alexandrian scholarship kinda just fell off the written record.
Jim probably refers to the 270s AD "guaranteed" destruction, now that I think about it. It fits way better with Merlin's proposed timeline (saving scrolls, starting the White council after the collapse of the Western Roman Empire, forming the Catholic Church during the Early Middle Ages, and keeping Amorrachius for Arthur (depending on which Arthur Jim is going with for the DV. The Historia Brittonum specifically mentions Arthur at the Battle of Badon Hill, which could have happened (if at all) anywhere from 430 AD to as late as 530 AD. Basically, Saxons invade, Arthur organizes resistance, the Britons win, and a Legend is born (though not written about for at least three hundred years)).
Though that gets all messed up if Jim adopts the Sarmatian/Lucius Artorias Castus theory, which has been popularized over the past several decades (based on wobbly evidence that really requires some leaps of logic) and is best known for producing the wonderfully fun and wildly inaccurate Clive Owen/Natalie Portman King Arthur film. It's worth watching for Mads Mikkelson's Tristan and Ray Stevenson being appropriately badass as Dagonet, at least. But that places Arthur at 410 AD and casts him as a Romano-Briton Auxilia Prefect.
The trouble is that the Sarmatian theory is based on a sarcophagus for Lucius Artorias Castus (whose Legion did serve in Brittanny) that's dated to 180-230 AD. It should be noted that this particular sarcophagus is in Croatia, so not exactly British Clay. It's based entirely on the idea that this particular Sarmatian officer was so popular in Britain that, centuries after his life and death, he was memorialized into a fictionalized account of the Battle of Badon Hill by Nennius—basically, Nennius created a hero out of a real dude who lived centuries ago.
In other words, the Sarmatian theory doesn't really work, as far as I'm concerned, so I hope Jim isn't going with the Artorias Castus concept.
That kinda got far afield of my original point. But yeah, it's probably during Emperor Aurelian's attack on Alexandria in the 270s that Merlin intervened.
