Clauses that start with as if / as though describe an unreal or improbable situation if they are followed by an unreal tense (the past subjunctive or the past perfect subjunctive). Otherwise, they express that the statement is true.
When we report conditionals and statements that refer to unreal situations, some tenses and modals may change if the reported words are no longer true or are out-of-date.
The past continuous subjunctive can be used in the if-clause of a sentence in the second conditional to express an unreal action in the present which is imagined as continuous:
The past perfect continuous subjunctive can be used in the if-clause of a sentence in the third conditional to express an unreal action in the past which is imagined as continuous:
