There are two different ways to say the time 9.45 pm in Spanish.
The first is to say the hour plus the minutes so nine forty five would be said:
"Son las neuve y cuarenta y cinco".
Alternatively, you could say "it is a quarter to ten", so you would say the following (which means fifteen minutes to ten in English):
"Son las diez menos cuarto"
How to ask the time in Spanish
To ask the time in Spanish you would say:
"Que hora es?"
Different times of day
To indicate that it is 9.45 pm in the evening you would add the word "noche" so the full sentence would read:
"Son las neuve y cuarenta y cinco de la noche"
For 9.45 am you would write (or say):
"Son las neuve y cuarenta y cinco de la mañana" De la mañana is in the morning"
How to tell the time in Spanish
The video below gives a good understanding of how to tell the time in Spanish.