Since the action described by past continuous is in progress at a specific time, you
need to specify the time, or the sentence ends up making no sense.
Check the examples to see what I mean:
Sarah was waiting for the bus last night.
Sarah was waiting for the bus.
The second sentence doesn’t really make sense, because it gives no context.
I was drinking tea when the burglar entered my home.
I was drinking tea.
Just like the example above, we can’t really understand the meaning of the second
sentence without extra information.
If you don’t specify the time, it’s impossible to
understand the meaning of a
sentence with the past continuous.
However, there is one exception: you can avoid specifying the time if you are
answering a question that already stated it:
I couldn’t call you
yesterday
, what happened? I was working overtime.
It is implicit that
the responder was working
yesterday
when the person asking
couldn’t reach them.
Combining past simple and past continuous
We use these two tenses together when we want
to talk about an event that
happened during the action expressed by the past continuous.
This construction emphasises the sentence in past simple and uses the past
continuous as a way to provide more information. You’ll mostly see these tenses
combined in stories.
Here are a couple of examples: