sometimes the jumping is very unresponsive and timing jumps is very difficult
Found a glitch which puts the time to zero. You preform it by collecting the milk and after that, falling into the void. After touching the voids death barrier you can press reset or next level on the completion screen. Now you will need to complete the level again without dying or pressing escape. If done right you can get the time display zero.You can get zero on every level except escape 1 (As far as I know). Tutorial and sandbox 0 was the hardest to get zero on.
update: i figured it out!
so what you have to do is get to the end of sandboxone and blowurself into the milk beating the level, but then wait for yourself to fall off the platform and die, then restart and you will have a menu infront of you, but you will be able to move, then hit esc or whatever your unpause key is, and the timer will be frozen! then you can just beat the level and get a time of 00:00:0