When using the subjunctive in if clause, do we describe a hypothetical situation in the past or in the present?
The subjunctive itself has no tense.
This is the same as the present participle. Despite present being in its name, it has no tense on its own; a helper verb needs to be used to place the action in time. (I was eating, I am eating, and I will be eating.)
A hypothetical event can also be placed in a similar temporal context:
- If you were to have taken the test, you would have failed.
A theoretical event in the past.
- If you were dead, I wouldn't be talking to you right now.
A theoretical event in the present.
- If you were to quit your job tomorrow, I would support you.
A theoretical event in the future.
The subjunctive itself doesn't determine the time of the event, but its placement in the surrounding sentence does.
The syntactical form is the past-tense were (or was or had, depending on style), but even though it's written as would be an actual past-tense verb, it's without tense.