I think Roman Catholics abstain from meat only on Ash Wednesday and every Friday of Lent, so I would assume they could eat meat the other days of April...
Why does "kwiecień" change to "kwietniu" here? Does using the "w" before it require a case change?
Yes, "w" meaning "in, inside" takes Locative. There are also situations when "w" takes Accusative.
Compare: "mam złamaną kość w nodze" (I have a broken leg in my leg, Locative), and "uderzyłem się w nogę" (I hit myself in the leg, Accusative. not even sure if "in" is the right preposition here).
Oh, btw: in April, in October etc. take Locative, but days of the week and the word "weekend" are exceptions and take Accusative despite using "w".
Because jeść in Polish is like many other verbs, that can mean both "I eat" and "I am eating".
We like sentences that are a bit strange semantically (especially using animals as the subject of the sentence), but well, there's also grammar :) And I was told by a native, that using Present Continuous makes very little sense here.
Quote 1: "It's weird... It's like I've known you as a vegetarian for a long time and you're telling me that you're going to start eating meat in April."
Quote 2: "The other possibility I can think of is that you're going to eat nothing but meat in April, which is also very unlikely and very weird, besides being unhealthy. :)"
And if I really meant one of those, I'd phrase it differently in Polish ;)
As far as I know, that would be a very strange sentence in English, so we do not accept it here.
I've encountered sentences like "my dog has a hat" before, so I thought strange sentences were the norm on here ;) immery seems to think its grammatically correct, thats why I'm confused.
From kwiecień becomes kwietniu? Well I need to be more focused on remembering polish vocabularies
If I were to say "Jem mięso w kwietniu" would this also be correct, but rather stressing the month rather than the action?