When you want to show my one-year-old nephew, Henry, a good time, all you have to do is say, "Boo!" If you get the cadence right, building up to the "boo" repeatedly in a rhythmic flow, Henry will collapse in spasms of unbridled laughter. This can go on indefinitely, until you both have to take a break in order to wipe your eyes and give your laughing muscles a reprieve.
Henry doesn't need to observe the Sabbath; he already lives there. He works hard—building vocabulary, developing mobility, eating crayons, laughing at aunts—and rests whenever the need for a nap seizes him. He doesn't yet reside in what the Greeks called chronos (chronological) time; he doesn't know a minute from an hour, or a calendar from a picture book. To Henry, the ticking of a clock is just another element of rhythm in the music of his life.
I believe Henry is still operating in kairos—the elastic, eternal present of God's time. The "boo" game goes on so endlessly because Henry has all the time in the universe. We grown-ups aren't so lucky.
Sabbath is, among other things, an invitation to periodically step out of the relentless stream of chronos in the hope of catching a whiff of kairos. It's a deliberate setting aside of to-do lists, an intentional surrender of the persistent delusion that the cosmos needs us to mind the store. It's a willingness to see time as a gift that need not be managed or maximized, but simply enjoyed. In fact, one of the telltale ways we know we've entered into kairos is the fact that when we do, we lose track of time altogether.