Sequence of Tenses - English Grammar Rules

The sequence of Tenses are the principles which govern the tense of the verb in subordinate clause vis-à-vis the tense of the verb in the principal clause. The rules which determine the tense of the subordinate clause if the tense of the principal clause is Present or Past or Future, is called Sequence of Tense.

Rules

1. If the principal clause is in the Past tense the subordinate clause should also be in the Past. Eg:

• My father assured me that he would buy a bike for me. 
• He failed because he didn’t work hard. 

Exceptions

1.  A Past Tense in the principal clausemay be followed by a Present Tense in the subordinate clause when the subordinate clause expresses a universal truth, mathematical calculation, historical fact, moral guidelines, habitual fact or something that has not yet changed. In such cases, the tense of the subordinate clause is not governed by the tense of Principal clause. (The subordinate clause is usually in Present tense in such cases). Eg: 
• He said that the earth revolves around the sun. 
• We learnt at school that the truth always triumphs. 
2. If a subordinate clause is introduced by a conjunction of comparison such as; than, as well as, etc. in such cases, a Past Tense in the principal clause may be followed by any Tense in the subordinate clause as per the sense of the statement. Furthermore, any tense in the Principal clause can be followed by any tense in the subordinate clause. Eg: 
• He loved me more than he loved you. 
• He loved me more than he loves you. 
• He loved me more than he will love you. 
• He will love you more than he loved me. 
• He has loved you more than he loved me. 
• He will love you more than he loves me. 
• She helps you as well as she helped me. 
3. If the subordinate clause is an adjectiveclause, in that case, it may be in any tense even the principal clause in Past tense. Eg: 
• I visited the place where the accident took place. 
• I visited the village where he lives. 
• I visited the hotel where he will stay. 

Rule 2. 

A Present or Future Tense in the Principal clause may be followed by any tense. 
Eg:

• He says that she passed the examination.
• He says that she will come tomorrow.
• Ram says that he likes that girl.
• Ram will say that Sita is a beautiful girl.
• Ram will say that he didn’t like that girl.
• He will say that he will pass the examination positively.

Exceptions

If the subordinate clause is introduced by if, till, as soon as, when, unless, before, until, even, if, as, etc. and the Principal clause is in Simple Future, in that case, the verb in subordinate clause must be in Simple Present.
Eg:

• We shall not go to market if it rains.
• He will wait till she comes.