sorry, I didn't know how to make tildes over the letters on my keyboard :D
To express At what time something is taking place we use:
Have a look and listen to the following examples:
Notice how "a" is always followed by the feminine definite article "las".
Now have a look at these other examples:
Notice how when something takes place at any time involving one (i.e 1:00 or 13:00 hours) the article takes the singular form "la".
It is not correct to say:
- Mi madre prepara el almuerzo a las una y media.
- Mi madre prepara el almuerzo a las una menos cuarto.
We also need the preposition "a" if we want to ask when something takes place:
Learn more about these related Spanish grammar topics
Examples and resources
Q&A Forum 1 question, 2 answers
So using la/las to indicate hour (hora), not the time (tiempo) that is why it's feminine? - A que hora? not A que tiempo?
That is a possibility as it is logical that if we are talking about "hora" (we do not use the word "tiempo" in this context), and hora is a feminine word. It is as if we were omitting the word "hora" when we say:
-¿A qué hora vas a llegar?
-A las 9 [horas].