It's quarter to six.
Is the way we say it.
10:05 is right
10:5 is very confusing. I might think you mean 10:50
1. It's a quarter to six.
2. It's quarter to six.
[I think two expressions are correct. Which one is commonly use in the USA?]
3. It is 10:05. It's ten o five. / It's ten oh five.
4. It is 10:5. It's ten five.
[Which one is grammatical, #3 or #4? Do we have to use 'o' or 'oh'?]
2 answers
Damon is right -- 2 and 3 are the correct ones.
It doesn't matter whether you write "o" or "oh" -- the sound is the same when you say that time aloud.
It doesn't matter whether you write "o" or "oh" -- the sound is the same when you say that time aloud.