Arch Chinese lists the meanings of 子 as

son, seed, egg, child, small thing, noun suffix(zi5), midnight, Kangxi radical number 39, 1st terrestrial branch

The meanings of child, egg, diminutive noun suffix etc. are clearly related, but I find it hard to remember that this also means midnight (in particular in the Korean 자정/子正).

How does 子 come to mean 'midnight'? Is it related to the fact that it also stands for '1st terrestrial branch'?

  • 1
    – tsh
    Commented Mar 2, 2019 at 7:48
  • 1
    Hi @tsh - I'm afraid I don't actually read Chinese - my interest in the characters is through learning Korean. Commented Mar 2, 2019 at 8:05
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    时辰 is an old time unit, 1时辰=2hours. A day is divided into 12 时辰 and we use 12地支(Earthly Branches) to name them. The first 时辰 in a day is from 23:00 to 01:00, which is called 子时.
    – tsh
    Commented Mar 2, 2019 at 8:28
  • Thanks. Sounds like that could be an answer to this question, unless you think there's already a duplicate answer on the site somewhere. Commented Mar 2, 2019 at 9:03

2 Answers 2


It is indeed related to the terrestrial (earthly) branches, and in a 24-hour day,「子時」represents the time of day between 11:00 PM to 1:00 AM.「子正」, as noted in the question, specifically represents midnight (12:00 AM).

Unfortunately, there is no convenient mnemonic or etymology that you can use to make a connection between「子」and midnight, but I doubt that midnight shows up very often anyway as a meaning (unless you're into traditional Korean timekeeping?).

  • I guess you could even say that 子 doesn't really "mean midnight", it's just a somewhat lazy/abbreviated way of explaining the notion behind 子时、子正
    – Fons MA
    Commented Jan 29, 2021 at 7:36

Maybe you should find some comparative charts of Chinese Zodiac/Earthly Branches to help you to remember them: enter image description here

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    It fits rather well into modern-day alcohol-induced-clubbing-weekend culture that the hours between 1 and 3 in the morning should be the ugly hours (in the PRC, at least). Though I guess for most, the real ugliness tends to be the following morning… Commented Mar 2, 2019 at 11:47
  • In Traditional Chinese Character, the earthly brach 丑 and 醜 (ugly) are two different characters...
    – Kholkhol
    Commented Mar 2, 2019 at 15:41
  • 2
    Hence why I said “in the PRC”, where simplified characters are used. Commented Mar 2, 2019 at 15:42

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