All the above clocks have one thing in common: they don't show seconds. They truncate down to the nearest lower whole minute, right? So when it's actually 14:15:45, they'll show 14:15.
And when the actual time goes from 14:15:59 to 14:16:00, then that's when your clock changes from 14:15 to 14:16.

They apply the floor function!