The ke (刻; pinyin: kè) is a traditional Chinese unit of decimal time lasting approximately a quarter of a western hour. Traditionally the ke divides a day into 100 equal intervals of 14.4 minutes (14 m 24 s). The ke is equivalent to the centiday, a non-SI prefixed unit. Ke literally means 'to etch' or 'to cut', and it is part of the noun Kedu which refers to etched-on markings on measuring devices.
Alongside the ke, the ancient Chinese kept time with double hours (traditional 時辰, simplified 时辰, pinyin shíchen) also known as watches. Because one cannot divide 12 double hours into 100 ke evenly, each ke was subdivided into 60 fen (分; pinyin fēn).
There were various attempts to redefine the ke to 96, 108, or 120 so as to divide evenly into 12 double hours. During the Qing dynasty around the time of the arrival of Jesuit missionaries, the duration of the ke was finally redefined to one ninety-sixth of a day, or exactly one quarter of a western hour. Today ke is the standard Chinese term to refer to a quarter of an hour. In addition, today's fen is currently used to refer not to 1/60 of a ke but rather 1/60 of an hour, or 1 minute.
- According to the Shuowen Jiezi from Xu Shen, “漏以铜壶盛水，刻节，昼夜百刻。” Translation: “Drop waters from a copper/bronze container with water inside. The time spent is measured. We can thus divide a whole day into 100 measures.”
- F. Richard Stephenson and David A. Green; Historical supernovae and their remnants, Oxford University Press, Oxford (2002), pages 15-16. ISBN 0-19-850766-6