"The train station was closed the entire month of June."
Translation:To nádraží bylo celý červen zavřené.
Czech does not have articles. To is a demonstrative (see the Tips and notes) and points to the specific train station, often referring back to the previous conversation and or to something we can see or similar. Often, but not always by any means, the demonstrative can be omitted when it is clear which train station it is or which boys they are. Here it can be omitted as well, but only in specific contexts where it is clear which train station we are talking about.
That I know. But I do not see the necessity for a demonstrative here? demonstrative pronouns, demonstrative adjectives. A pronoun is a word that takes the place of a noun. A demonstrative pronoun is a pronoun used to point something out. The demonstrative pronouns are this, that, these and those.
Is there an explanation somewhere about when prepositions can be omitted in Czech? In the structure of this sentence, the subject is "The train station", "closed" is an adjective describing the station, and "the entire month of June" is an adjectival phrase describing the closure, which in English would normally (but optionally) be introduced by a preposition such as "for" or "during". Here that preposition is missing in both the English and the official Czech translation. In English, which is quite a sloppy language, such prepositions can quite often be left out without anyone bothering about them, like here, but I was under the impression from previous exercises in this course that Czech is more particular.
There are no such general rules. Some expressions require specific prepositions, some use no prepositions. These temporal adverbials can be used without prepositions in both languages. One can also say "po celý červen", but that does not mean that just "celý červen" is made from "po celý červen" by ommiting the preposition, it is just another way how to phrase it.
It's accusative. There is no "month of June" in the Czech sentence, only "June". The "month of June" is only in the English sentence. That would hypothetically be "měsíc června" but that just doesn't work in Czech at all.
I'm not sure how English would like "the entire June" or "the whole June" - it does work colloquially.