"Tuesday is her birthday."
Translation:El martes es su cumpleaños.
From what I've seen/heard so far, I believe that the days of the week all have to begin with "el" in Spanish, correct me if I am wrong..
Well, from what I know, "el" before the name of the day is added when you say about something happening on given day on regular basis. Here it should not be obligatory, although maybe it is because it is "This Tuesday" in fact, not any Tuesday
I never hear it spoken this way. I hear it usually.with cumple being a verb, as in "she completes her year on Tuesday."