Contextual time: Past Continuous is used for ongoing actions even if period or point in time is not indicated. Usually it happens when there is no need to explicitly show the time. This is because it’s just not important or we can easily infer time from the context.
Sorry, I wasn’t listening.
In the above example we can understand that at the time one person was talking, the other one wasn’t listening. So, the time is actually inferred by contextual means. In this example the period or point in time is another implicit ongoing past action. This falls into another use of Past Continuous – parallel actions.
Why didn’t you come? – I was preparing for my exam.
Also, in the above example, the time is inferred from the conversation. The speaker could mean morning time, exact time, a period of time etc:
I was preparing for my exam while you were celebrating your birthday (another continuous parallel action)
I was preparing for my exam when it happened (another short action – perpendicular action)
I was preparing for my exam all morning (period in time)
I was preparing for my exam on the 22d of January (date)
I was preparing for my exam on your birthday (event)
I was preparing for my exam at 3 pm (exact point in time)
I was preparing for my exam from 3 to 7 pm (period in time)
That’s why I didn’t come.
In this example the time is not explicitly shown, however, the two speakers know exactly what time they are talking about.
In conclusion, contextual time in Past Continuous
period of time
Past Continuous with contextual time has 3 conditions:
1. Action takes place in the past
2. Action is not complete, i.e. continuous
3. Action happens during time period and this period is not in the sentence, but we can infer it from the context. Action happens during contextual time.
Also on Past Continuous: