While doing counting topics, most of my students would shout out to me “the Chinese language makes so much sense!”with a big smile on their face. When it comes to describing a.m. and p.m. in time, they would frown a bit, ask a few questions about pronunciation and say “I guess I just have to memorise it” with a sigh.
It is true that the a.m. and p.m. are much more complicated in Chinese, and the reason goes back to the ancient times where people divide one day into 5-hour blocks（更 gēng）, 2-hour blocks（时shí 辰 chén) and 15-minute blocks（刻 kè)。
You can refer to the picture below for the names of different “time zones” in one day:
The typical cut off point for 早(zǎo)上(shàng) and 上(shàng)午(wǔ) is about 10:00am.
So, if you’d like to be accurate about telling time in Chinese, instead of only saying 三(sān)点(diǎn)，add in the “time zones” by saying
下(xià) 午(wǔ) 三(sān) 点(diǎn) for 3:00p.m. and
凌(líng) 晨(chén) 三(sān) 点(diǎn) for 3:00a.m.,
as the native Chinese are not so used to say 15点(diǎn).
It’s about time to tell your time right and avoid any miscommunication.