Code:
var kickoff = new Date(2015, 0, 3, 10, 30, 0, 0)
var diff = kickoff - new Date()
var d = Math.floor(diff/1000.0/60.0/60.0/24.0)
diff -= d * 1000 * 60 * 60 * 24
var h = Math.floor(diff/1000.0/60.0/60.0)
diff -= h * 1000 * 60 * 60
var m = Math.floor(diff/1000.0/60.0)
diff -= m * 1000 * 60
var s = Math.floor(diff/1000)
dDiv.innerHTML = d
hDiv.innerHTML = h
mDiv.innerHTML = m
sDiv.innerHTML = s
document.title = d + " Days Until Kickoff"
Here's how I did it, just a little bit easier to read and modify. The -= vs %= difference for the calculation is interesting.