"Forty days of camping are hard."
Translation:Quaranta giorni di tenda sono pesanti.
Actually no :-) - grammar is very rarely a question of dialect. You may say "40 days of camping are hard", but that doesn't make it grammatically right, in my opinion. If you say "camping is hard" and then add "40 days of camping is harder", you can see my point. The talk is not about 40 individual days, but about a long period. If you say "40 days of camping are hard days" it's another matter, of course.
So would you also say 'The family is having dinner' is correct, whereas 'The family are having tea' is wrong? Both are correct, but depending on what you are used to one or the other might sound unnatural (perhaps because we are in different places of the world, where they speak different dialects).