Asking and telling time is simple once two words are separated: 点 for o'clock times, 小时 for durations. Mixing them is THE time-telling error.
Clock time
Hour + 点 + 分： 三点十五分 = 3:15. Shortcuts: 半 (half) replaces 三十分 - 三点半 = 3:30; 刻 (quarter) is more literary - 一刻/三刻 appear but 十五分/ 四十五分 are safer. "Five to three" runs as 差五分三点 (lacking five minutes to three) - the 差 frame.
AM/PM and the daily blocks
No "am/pm" - time words qualify the hour: 早上六点 (6am), 上午十点 (late morning), 中午十二点 (noon), 下午三点 (3pm), 晚上八点 (8pm), 凌晨两点 (2am, wee hours). Context usually disambiguates; add the period word when it matters.
Duration ≠ clock
The split that matters: 三个小时 = "three hours long" (duration), 三点钟 = "three o'clock" (a point). 我们学了两小时 - we studied two hours; 两点见 - see you at two. Asking: 现在几点？ vs 多长时间？ - "what time is it" vs "how long".
Phrases that carry it
几点见？ (what time do we meet), 还有多久？ (how much longer), 来不及 (won't make it), 来得及 (will make it), 迟到 (be late), 早到 (arrive early). The numbers themselves: the numbers guide.
Digital and 24-hour time
Written time often uses the colon: 15:30, spoken as 下午三点半 or, formally/officially (stations, schedules), 十五点三十分 - the 24-hour form exists but mostly in announcements. 一刻 and 三刻 are the traditional quarters; younger speakers mostly say 十五分/四十五分. For "a quarter to": 差一刻三点. Timetables and the 12306 rail app run on the 24-hour format - worth recognizing even if you speak in 上午/下午.
Common questions
How do you ask what time it is in Chinese?
现在几点？(xiànzài jǐ diǎn) - literally "now, how many o'clock?" 几 replaces the unknown hour.
What is the difference between 点 and 小时?
点 marks clock points (三点 = three o'clock); 小时 marks duration (三个小时 = three hours long). The most common time-telling mixup.
How do you say "a quarter past" in Chinese?
Three options: 三点十五分 (3:15 literally), 三点一刻 (the 刻 = quarter), or less formally 三点十五. All understood.