"Today is impossible for us."
Μετάφραση:Σήμερα είναι αδύνατο για μας.
Το σήμερα. The gender is neuter and not feminine (there are some nouns that end in α but are neuter. Το νήμα/κύμα/πέρασμα/σήμερα/βλέμμα/ψέμα/αποτέλεσμα...). Don't get tricked. ;)
(Also, I do believe there is a bit of a mistake in that sentence. "Today is impossible for us" translates to "Το σήμερα είναι αδύνατο για μας." At least, it makes much more sense to me this way. However, I do believe that the english sentence was meant to be "Today it's impossible for us.", where αδύνατο refers to it, and not to σήμερα.)