The trick answer is "a riddle". There are also many other applicable solutions posted as comments. However, the answer that I had in mind when I wrote it was...
Time is a force to be reckoned with whenever there is a desire to change the past or create more of the present or future. An example, "you can't hold back the hands of time."
As we get old and get tired and retired, time is always moving. And as long as we seem to exist, it seems to exist.
Time has many definitions and a great singer once performed the desire to put "Time In A Bottle". Tragically, the desire was unsuccessful.