n.

1. 时间的选择（或安排）
2. 计时

n.

1. the choice, judgement, or control of when something should be done.
2. a particular time when something happens.
   ▸(in an internal-combustion engine) the times when the valves open and close, and the time of the ignition spark, in relation to the movement of the piston in the cylinder.