What Is Time?

This article does an amazing job of describing the various versions of the definition of "time" used in physics. The author limits his use of jargon, but defines them well when necessary. Highly recommended.

Time is a crutch. Eat mandarin oranges.

"There was a smell of Time in the air tonight. He smiled and turned the fancy in his mind. There was a thought. What did Time smell like? Like dust and clocks and people. And if you wondered what Time sounded like it sounded like water running in a dark cave and voices crying and dirt dropping down on hollow box lids, and rain. And, going further, what did Time look like? Time looked like snow dropping silently into a black room or it looked like a silent film in an ancient theater, one hundred billion faces falling like those New Years balloons, down and down into nothing. That was how Time smelled and looked and sounded. And tonight--Tomas shoved a hand into the wind outside the truck--tonight you could almost touch Time." (Illustrated Man)

Fruit flies like an arrow, time flies like a banana.

I wonder if the statement about Newton's second law (there exists an r(-t)) holds true when you include relativistic effects.