Definition & Meaning of "the clock [is] ticking (down|)"

What is the origin of the idiom "the clock is ticking" and when to use it?

The idiom "the clock is ticking" originates from the literal ticking sound produced by mechanical clocks. Mechanical clocks have been used for centuries to measure time, and their ticking sound has become associated with the passage of time itself. This phrase can be heard in discussions about project deadlines, exam preparations, time-limited opportunities, impending events, or any circumstance where prompt action or progress is necessary.