Verb tense and sequence

A finished time expression — in 2018, yesterday, last month, two years ago, during the war — forces the simple past. The present perfect needs time that is unfinished or unstated: recently, so far, already, yet, ever, never, since, this year.

For takes a length of time, since takes the point it started. Since also introduces a clause in the simple past while the main verb stays perfect: Since she joined the department, output has doubled.

Two past events, one clearly first: the earlier one takes had + past participle. Triggered by by the time, before, after, already, until then, previously. Where the order is obvious from the sequence alone, the simple past is enough: She opened the door and walked out.

After a past reporting verb, each tense moves one step back: present → past, past → past perfect, will → would, can → could, must → had to. Time words shift too: tomorrow → the following day, now → then, yesterday → the day before. A permanent truth may stay unshifted: He said that water boils at 100°C.

After when, as soon as, before, after, until, once, by the time, future meaning is carried by a present form. Use the present perfect for a completed step: Once you have submitted the form, you will receive a code. The exception is when meaning at what time in a direct or indirect question, which does take will.

The three pairs TOEFL tests: if + present → will; if + past → would; if + had done → would have done. Would never appears in the if-clause. Watch for mixed conditionals, where a past condition has a present result: If they had invested earlier, the company would be profitable now.

Regret about the past takes the past perfect; a wish about the present takes the simple past. Wish + would is reserved for complaints about other people's behavior: I wish he would stop interrupting. The same past-for-present logic drives if only, would rather you came and it's time we left.

Use the perfect continuous when an activity ran up to now and the duration matters. Use the plain perfect when the result matters or the amount is counted: She has written three chapters (result) against She has been writing all morning (duration).

Verbs of thinking, feeling, possession and perception avoid the continuous: know, believe, understand, own, belong, contain, consist, seem, appear, prefer, need, resemble. A few change meaning rather than break the rule: I am thinking about it (activity) against I think it is wrong (opinion).

By + a future point calls for the future perfect: the action is complete before that moment. The future continuous marks something in progress then: This time next week we will be presenting the results. Keep both apart from going to for present evidence and intention, and will for a decision made as you speak.

Three separate structures. Used to + base form is a discontinued past habit or state. Be used to + -ing means accustomed to and works in any tense. Would + base form also narrates repeated past actions, but not past states: She would walk to school is fine, she would live there is not.

Do not change tense mid-passage unless the time frame really changes. Two conventions matter for TOEFL writing: plots, arguments and what a text says are described in the present (the study argues, the novel opens), while what researchers did and found is reported in the past (Kuhn surveyed 400 cases).