"это" там точно есть? Не лучше ль без него?

Это был яркий холодный апрельский день, и часы пробили тринадцать.

Да, точно.
Добавлю всё-таки вариант без "это", так как вне контекста он более удобным мне видится.

I didn't mean to suggest that "Это" needs to be there, but simply to refer to the end of the sentence, where I found "и часы пробили тринадцать" instead of the above wording.

Yeah, that wording is quite closer to the original and also smooth.
I think this sentence could be modified according to your findings, and the other sentence would be its double but for the first word (useful for learners, I think, showing that the formal subject may or may not be present in a sentence like this).

Do we need to add only official translations from the book, or also variants according to our own translation? I guess everyone can add a translation of his or her own. Yes, I also find it better looking without "Это" (but this I add as a non-native speaker ;-) ).

Our comments occurred almost simultaneously, so I guess you referred to something to which I also referred almost at the same time. Anyhow, I concur. ☺