"The weather is beautiful this weekend."
Translation:Il fait beau, ce week-end.
I agree. Fin-de-semaine is perfectly acceptable, in France as well as Quebec.
Au Quebec, on dit 'fin-de-semaine', pas 'week-end'. Ça devrait être accepté aussi.
Why it is wrong: "Le temps est beau, cela week-end"? It said I should use "ce" instead of "cela". Why I cannot use "cela" here?
Because cela is a pronoun, not a determiner, if I have my 'parts of speech' right. "This" acts like an adjective - 'this' weekend, not 'that' weekend. Cela, on the otherhand, can only function like a noun. So, it's more like 'this thing' or 'this one' or (literally), 'this, here' (imagine I'm standing here pointing at it).
So, you can say "Cela est beau": "this is beautiful" as in "this thing, here, is beautiful". Or you can say "Cette chose la est belle" (cette = feminine ce). But you can't say "cela chose est belle".