Why do we use past tense after "it is high time"?

Why do we use past tense after "it is high time"? I isn't always sued with the past tense. You can say "It is high time that you pick up the clothes in your room." "It is high time that you start studying for your exam."

Why do we use past tense after "it is high time"? The reason is in the meaning of it is high time it is informal. and is used to say it is time to do something that should have been done a long time ago. It's high time you got a job It's high time be bought a new car So neither thing has happened yet but they should have happened sometime in the past, hence as use the past tense after it.