The sequence of tenses is a fundamental concept in English grammar. It explains how the tense in the main clause influences the tense in the subordinate clause. Here’s a quick guide:

• Main clause – Past tense; Subordinate clause – Past tense
• Main clause – Past tense; Subordinate clause contains universal or habitual facts – Present/Future
• Main clause – Present/Future; Subordinate clause – Any tense
• Conjunction of purpose: Main clause – Present/Future; Subordinate clause – May/Might
• Conjunction of purpose: Main clause – Past; Subordinate clause – Might
• Lest + S + should + V1: Any tense in main clause; Subordinate clause – Lest Should
• Conjunction of comparison: Any tense in both principal and subordinate clauses
• Comparison expressed by ‘as well as’: Any tense in both clauses
• If no verb after ‘than’ or ‘after as well as’: Tense in the subordinate clause is the same as that in the principal clause