“What time is it?” is the phrase to use whenever you want to know the time. In English, as well as in Portuguese, there are numerous ways to tell the time.
Ex.:
1:00 – It’s one o’clock. (It's one hour sharp).
3:00 – It's three o'clock. (It's three o'clock sharp).
2:20 – it's two twenty. (It's twenty past two).
5:40 – It's five forty. (It's five-forty).
Note: The "o’clock” is only used for exact times. E.g.: 1:00, 4:00, 10:00.
To understand split hours it is necessary to imagine a few things.
1st – Imagine that this circle is a pizza.
2nd – If we eat the whole red part of the pizza, it can be said that we will have eaten ½ (a half).
3rd – Now imagine that this pizza is a clock. How many minutes correspond to "the half”? "A half” corresponds to 30 minutes.
Well, in English, we can say it's eight thirty (it’s eight-thirty) or that it is half past eight (It's half past eight).
Ex.:
4:30 – It's four thirty (It's four-thirty).
It's half past four. (It's half past four).
2:30 – It's two thirty (It's two-thirty)
It's half past two. (It's half past two).
Now let's continue to imagine that circle is our pizza. If I take ¼ (a quarter) of this pizza, how many minutes is “a quarter”? “A quarter” equals 15 minutes.
On the clock above you can see that it is 6:45 (It's six forty-five), or we can still say that it's a quarter to seven (It's a quarter to seven).
Ex.:
2:45 – It's two forty-five. (It's two forty-five).
It's a quarter to three. (It's a quarter to three).
9:45 – It's nine forty-five. (It's nine forty-five).
It's a quarter to ten. (It's a quarter to ten).
What if it was 4:15? In Portuguese, we say it is four-fifteen; in English, in addition to this form used, they also say that it is a quarter after four, which would be equivalent to saying: (It's a quarter after four).
Ex.:
8:15 – it's eight fiftteen. (It is a quarter past eight).
It's a quarter after eight. (It's a quarter past eight).
11:15 – It’s eleven fifteen. (It's a quarter past eleven).
It's a quarter after eleven. (It's a quarter past eleven).
Another resource used to tell the time is “a.m” and “p.m”, both are expressions that originated from Latin. “Am” indicates “anti meridium”; and p.m, “post meridium”. You should use “a.m” to indicate the hours before noon, or better, to express all hours from midnight to noon. The “p.m” must be used for the hours after noon, or even for all the hours between noon and midnight. So, if it's three o'clock in the morning, we should say: It's three a.m, if it's three o'clock in the afternoon, we should say: It's three p.m.
Layssa Gabriela Almeida e Silva
Brazil School Collaborator
Degree in Languages - English from the State University of Goiás - UEG
Improvement course in English by Zoni Language Centers - USA - USA
English - Brazil School
Source: Brazil School - https://brasilescola.uol.com.br/ingles/what-time-is-it.htm