[kybernetyk]

Heh, funny. I recently implemented a countdown for a teleprompting app and that's exactly what I ended up doing to make the countdown "feel right".

The countdown in question doesn't display fractions of a second so it would immediately switch from "5 seconds left" to "4 seconds left" which just doesn't feel right. Adding 0.5s solved the issue.

[fainpul]

Just round up. The countdown is done as soon as 0 appears (0 doesn't linger for 1 second).

[happytoexplain]

To expand a bit on what others have said:

If you're counting up, round down. If you're counting down, round up. A human expects the count to finish at precisely the moment we get to the last number in the sequence (zero, for counting down). Do a count in your head to see what I mean.

Apple chose a compromise by rounding to nearest, for it to "feel good", but you lose the ability to exactly predict when the timer ends as a human. Typical Apple.