How to express time in English? To be more specific, you'd better talk about grammar.

On the hour: one o'clock. It means one o'clock. Everything else is the same ...

It's a quarter past one. Quarter means 15 minutes or a quarter. Two quarters means 1: 30, and three quarters cannot be used (explained below).

It's half past one. It means half past one. Half means half.

I used it 30 minutes ago, 1: 24, and now it's 1 point 24.

After 30 minutes, use to, but after 30 minutes, it means how many minutes to what time. For example, 1: 45, a quarter to two. It's two fifty-six, four minutes to three.

There is also the simplest way in the United States: look at the time directly. For example, it's two thirty-five.