I came across the usage of subjunctive the other day. I read that if the main verb is in the present, future or perfect with have, the subjunctive is in the present whereas if the main verb is in the past, the subjunctive is in the imperfect.
Is it possible for the subjunctive to be in the future?
The subjunctive is also known as conjunctive — these two words are synonymous in Latin grammar. The subjunctive mood has four tenses: present (faciam), imperfect (facerem), perfect (fecerim) and pluperfect (fecissem).
The indicative mood has two more tenses: future and future perfect. While the subjunctive does not have these tenses, there is a replacement, known as periphrastic forms. I suggest taking a look at this older question regarding the future perfect subjunctive.
So, to answer your question, there are no future subjunctive forms in Latin, but there is a decent replacement. In the passive voice you have to use the present tense instead — or the perfect tense to replace future perfect. I don't know if the active periphrastic conjugation is a must in subordinate clauses when possible. (I asked a separate question about this point.)
In many subordinate clauses the tense of the subjunctive predicate depends on two things: when does the "subordinate action" take place with respect to the "governing action", and what is the tense of the governing clause.
If the governing clause refers to present or future things, then the predicate of the subordinate clause with subjunctive mood is
Similarly, if the governing clause refers to the past, the tense of the subjunctive is imperfect/pluperfect/imperfect in the order of the above list.
