Why does this sentence have an ablative subject for an indirect subordinate clause?

Question

In this sentence, hoc anno is the subject of esse, so I expect it to be in the accusative, "hunc annum". Also, futura should agree in gender to annus, masculine. What am I missing?

(If it's not obvious, this is the blurb for Harrius Potter et Camera Secretorum.)

Harrius Potter est magus. Discipulus est secundarius Scholae Hogvartensis Artium Magicarum et Fascinationis. Vix scit hoc anno tot miracula futura esse quam anno proximo

Harry Potter is a wizard. He is in his second year at Hogwarts School of Witchcraft and Wizardry. Little does he know that this year will be just as eventful as the last . . .

Answer 1

The accusative subject of the sentence you highlight is actually tot miracula. Let's go through it step by step:

Vix scit...

He hardly knows that... [setting us for an accusative + infinitive]

tot miracula futura esse

...as many wonderful things are about to happen...

hoc anno...quam anno proximo.

...this year as last year. [ablative of time when]

The tot sets up a comparison, which is normally done with the correlating pair, tot...quot: "as many...as." I have never encountered tot correlated with quam in this way, nor can I find any mention of this construction in Lewis & Short, so I suspect it's just a clumsy translation.

Answer 2

In this sentence, hoc anno is not the subject of esse. The subject of this infinitive is tot miracula (Acc. pl.). I'm afraid what you're missing is the following fact: you should not expect translations respect the syntax/grammar of the original text. Generally speaking, good translations must respect the meaning/contents/information but not necessarily the syntax/grammar of the original text. In the English text "this year" is the subject of the verb but you should not apply the very same syntactic analysis to the Latin sentence.