Here is the full list of all 5 A long Time achievements. It takes around 0-1 hour to unlock all of the achievements on Windows.
You fell and respawned. You don't have time to fool around. Look at the angry red Clock.
You entered a very strange room.
Time bends and stretches. Yes, this counts for Clocks, too.
That is a Clock? I can't even see the end of it!
It's been a long Time, but we're done now.