1. Sequence of Tenses

2. Sequence of Tenses
There is a logical sequence of tenses as the speaker or writer proceeds from the main clause to the subordinate clause.

3. Primary Tenses
A PRIMARY tense of the indicative (in the main clause) must be followed by a PRIMARY tense of the subjunctive (in the subordinate clause).
The primary tenses of the indicative indicate INCOMPLETE action (actions now going on (PRESENT) or to be begun in the FUTURE.

4. PRIMARY TENSES
The primary subjunctive tenses used in the subordinate clause are:
Present
Perfect

5. SECONDARY SEQUENCE
The secondary tense of the indicative must be followed by a secondary tense of the subjunctive.
The secondary tenses refer to past actions.

6. Secondary Sequence
The subjunctive tenses used in the secondary sequence are:
Imperfect
Pluperfect

7. SEQUENCE
MAIN VERB (INDICATIVE)
SUBORDINATE SUBJUNCTIVE (time of action relative to main verb)
PRIMARY
PRESENT OR FUTURE OR FUTURE PERFECT
PRESENT (AT SAME TIME OR AFTER)
PERFECT (ACTION BEFORE)
SECONDARY
PAST TENSES (IMPERFECT, PERFECT, OR PLUPERFECT)
IMPERFECT (AT SAME TIME OR AFTER)
PLUPERFECT (ACTION BEFORE)