The word clock appeared first in English in the 9th century but at first it didn't mean a device for measuring time.

9世纪时英语中第一次出现了“ clock”这个词，但最初这个词并不表示计时的器具。

youdao

Sure, oh, 7 o 'clock in the morning. I mean the local time.

当然，哦，是早晨7点，我是指当地时间。

youdao

2 o 'clock in the afternoon, I mean the local time.

下午两点，我指的是当地时间。

youdao

Over a few decades this would amount to a minute's difference, but over several hundred years this would mean the atomic clock time-scale and the time-scale based on the Earth's rotation would be out by an hour.

BBC: Changes to the world's time scale debated