"My birthday is in July."
Translation:Moje urodziny są w lipcu.
urodziny it is plural always, jest is for singular : to jest kobieta , to są kobiety
Well, that means that you've been talking about July (and so it happens that you were born in July), not talking about your birthday (which is in July).
But... okay, added.
What gender is urodziny? Wiktionary does not specify, so I was wondering if "Mói urodziny są w lipcu" would also be correct, or if there is a rule for this word?
It's 'not masculine-personal plural'. This word has no singular form.
And "mói" is not a word, I guess you meant "moi", but it's the wrong plural.
I think I tried it without moje too, but rejected the shorter 'Mam urodziny w lipcu' as well.