I actually really liked the little anachronisms of A Series of Unfortunate Events because it adds to the subtle absurdity and abstraction of the story space.
The whole narrative perfectly constructs this slightly ‘off’ world where three orphans can somehow be passed around the same group of (barely disguised) people from place to place, an infant child can become a gourmet cook before learning to form sentences, etc. In this world, evil is both carried out and vanquished by complete chance, or the intervention of deus ex machina that actually never feels out of place because of just how weird everything else is. Why wouldn’t a Scooby Doo-esque button be concealed in a village statue in a world where a man can burn a mansion down with a strategically placed mirror? Why not have a narrator define words at random, but only ever in a single context, if said narrator is also going to devote an entire page to the word ‘ever’?
It’s just the same with the date; the things that happen to the Baudelaire children are the product of a backwards world, and in their perennial adolescence they too seem to be a little unstuck in time. Count Olaf has an outdated title, but despite being anchored to this by his very name he floats between a frankly unmatched number of false identities. It’s just one of many characteristics of a series that does the absurd/unsettling exceptionally well at every level.