Admittedly, it has been a very long time since I've studied Spanish, but I distinctly recall that we always used "¿Que hora es?" for "what time is it?".
However, on a trip to the Dominican Republic, I asked our tour guide "¿Qué hora es?", and he corrected me, saying "¿Qué horas son?" is the internationally recognized proper grammar. He mentioned that he was training to be a multilingual instructor of Spanish, English, and German, and that his phrasing was authoritatively correct per his training.
I find the phrasing of that strange, not only because I was taught the other way. My literal translation of that seems to be "what hours are they?". The tour guide's explanation was that the hours of the day are plural, and therefore using the singular is incorrect. However, to my mind the "¿Qué hora es?" form is asking "what hour is it?", as in "it is the 5th hour", which makes more sense to me than "there are 5 hours".
Is one phrase correct and the other incorrect, or are both acceptable? Also, is my understanding of the translations correct (i.e. "what hour is it" vs. "what hours are they")? If "what hours are there" is the correct translation, why is "qué" used instead of "cuántas"?