Use of it is time / high time

It is time + past subjunctive (unreal past)

It is time can be followed by infinitive:

It is time to start.

or

by for +object + infinitive.

It time for us to move forward.

It is time for us to earn money.

It is time for me to go to school,

It is time for me to buy the book.

It is time for us to go.

 or

by subject + a past subjunctive

It’s time we went.

It is time we prepared for the examination.

It’s time we were leaving/ going.

There is somewhat difference in meaning between the forms.

it is time + infinitive only refers that the right time has come.

It is time to go there.

It is time to join in the job.

It is time to read.

It is time to finish the duty.

it is time + subject +past subjunctive indicates that it is somewhat late.

high can be added to emphasize this idea.

It is high time + subject + v. past form + ob +extension.

It is high time we left the place.

It is high time I learnt the lesson.

It is high time we helped him.

It is high time we met the officer.

It is high time they took exercise.

It high time we wrote the notice.