This is a question sentence and it means "How many months does one year have". (Cuantos = How many; meses = months; hay = there are; en = in; un = one; ano = year).
How many weeks are in a year? 52...
How many seasons are there in one year?
"How many days are there in a year?"
Hay 365 días en un año común y 366 días en un año bisiesto.
4 estaciones
it means "how many years is it?" or "..... are there"
It means"How many teachers are there?"
"¿Cuantos dias hay en septiembre?" is Spanish for "How many days are there in September?"
How many days are there until...
That means "How many are there in an hour?"
If the sentence says "¿Cuántos días hay en un año? it means "How many days are there in a year?" If it says "¿Cuántos días hay en una semana? it means "How many days are there in a week?"
cuantos dias hay en una semana