Rule 5.3: Time Clauses - the Past Simple vs the Past Progressive
Expressing past time using time clauses

We can show that two ideas are related to each other and also linked to a specific time within the same sentence. There are many times when the Past Simple and Past Continuous are seen in the same sentence. There are also many examples of two clauses using only the Past Simple. This structure usually indicates that the two clauses, or subject + verb structure, are somehow linked. The two ideas are related.

a) When I went to Regina, I visited my aunt.

b) I visited my aunt when I went to Regina.

when I went to Regina = a time clause*
I visited my aunt = a main clause*
(a) and (b) have the same meaning.
A time clause can:
1. come in front of a main clause, as in (a);
2. follow a main clause, as in (b).
c) After Francois ate dinner, he went to the movies.
d) Francois went to the movies after he ate dinner.

e) Before I went to bed, I finished my homework.
f) I finished my homework before I went to bed.

g) While I was having a shower, the phone rang.
h) The phone rang while I was having a shower.

i) When the phone rang, I was having a shower.
j) I was having a shower when the phone rang.

When, after, before, and while introduce time clauses.

when/after/before/while + subject and verb = a time clause

Punctuation: Put a comma at the end of a time clause when the time clause comes first in a sentence (comes in front of the main clause):

time clause + comma + main clause

main clause + NO comma + time clause

l) When the phone rang, I answered it. In a sentence with a time clause introduced by when, both the time clause verb and the main verb can be simple past. In this case, the action in the “when clause” happened first. In (i): First: the phone rang. Then: I answered it.