high time

English as a Second Language English Vocabulary, Grammar and Idioms
1
  1. Let’s go home.
  2. It is high time that we went home.
    Does #2 mean #1?
    Please explain with the related nuance of grammar.
  3. It was high time he had gone to college.
  4. It was high time he went to college.
  5. It is high time he went to college.
  6. It is high time he goes to college.
    Are they correct?
    Please explain the difference in meaning between them.
    Thanks.
2

2 is more emphatic than 1. It means we really ought to be going home right now,

3 and 6 are incorrect due to the tenses.

The difference between 4 and 5 is purely in the main tense. ‘Went’ can be used in the second part with both past (was) and present (is) because we can use the expression it’s time + subject + past verb form to refer to the present.
Similar structures can be found here:
learnenglish.britishcouncil.org … if-clauses