in latin, the sequence of tenses rule affects dependent verbs in the subjunctive mood, mainly in indirect questions, indirect commands, and purpose clauses. if the main verb is in one of the non-past tenses, the subordinate verb is usually in the present or perfect subjunctive (primary sequence); if the main verb is in one of the past tenses, the subordinate verb is usually in the imperfect or pluperfect subjunctive (historic sequence). for example, when the subordinate verb refers to a time contemporaneous or later than the time of the main verb, the present or imperfect subjunctive is used: