Are you smart enough to explain time to a fifth grader?

Nick Williams' winning entry in the 2013 "Flame Challenge." an international kid-judged science contest sponsored by Stony Brook University on Long Island, NY, and actor Alan Alda:

What is time?

Have you ever heard your parents say to you that it's time to go to bed or time to get up, time to go to school, time to clean your room, time to do this, time to do that, and on and on. Our world runs on a time schedule, and the schedule is so tight that there are schedules for everything we do throughout the day and clocks that tell you what time it is so we can do those things at the correct time. Time is so obvious in our lives that no one questions it. It's just there, we have to live with it, and so we accept it. All activity on earth is based on time, and this time is what happened a second ago, a minute ago, an hour ago, days ago and years ago. Well, now we have an important question. What is it?

Time has a lot of definitions, like time is history or time is age. But, have we ever considered a good definition? I have. Here's my definition. And no, I did not get this from some book or online. It's just something that makes sense to me. I think of time as Forward Movement. Think about it! Everything moves forward, from the universe to every second of your life. And because everything moves forward, man developed a way to keep track of this Forward Movement and called it time. Man also invented clocks to keep a precise log of this Forward Movement in years, days, hours, minutes, seconds, and even parts of seconds. I'll always continue to think of time as Forward Motion. I'll also think of it as a Forward Motion that will never change, will never stop and can never be reversed.

Source: Nick Williams