It was imperative that he found a job. vs It was imperative that he find a job.

[*Rahul*]

I read somewhere that it does not matter whether the sentence is past or present subjunctive mood remains the same.

Which one is correct and why???

I wish I knew him
I wish i know him

It was imperative that he found a job.
It was imperative that he find a job.

The president requests that they stop it quicky.
The president requested that they stop it quickly.

please elaborate

Regrads

[Mister Micawber]

I wish I knew him
I wish i know him-- 'Wish' must use the subjunctive, so the 2nd is wrong; it is indicative mood.

It was imperative that he found a job.
It was imperative that he find a job.-- The 'it is imperative/important/etc form does not know require the subjunctive, so both are fine, as is 'It is imperative that the finds her'.

The president requests that they stop it quickly.
The president requested that they stop it quickly.-- This seems to be the only pair that illustrates your point about present/past. Yes, both are fine.
_________________
Native English teacher at Mister Micawber's

[*Rahul*]

but don't we say in desire,proposal,wish we use present subjunctive when the tense in the sentence is either present or past

[Mister Micawber]

No.

I wish I knew him.
I wished I had known him.
_________________
Native English teacher at Mister Micawber's