Guide to English grammar

It hasn't been very warm today.
I haven't seen much television this week.

4 We often use for and since with the negative present perfect.

I haven't skied for years. /I haven't skied since 1988.
We can also use since with a clause.
I haven't skied since I was twelve.
Compare the past simple.
I last skiedyears ago/in 1988/ when I was twelve.
We can also use a phrase with for with the past simple to say how long something went on.
I skied for hours.

2 Use
1 An action over a past period

We use the past continuous for an action over a period of past time, something that we were in the middle of.
At quarter to eleven I was walking home.
The UFO was travelling east to west.
I wasn't sleeping, so I got up.
I looked into the room. All the old people were watching television.
Compare the present continuous and past continuous.
The UFO is travelling west. (It is in the middle of its journey.)
The UFO was travelling west. (It was in the middle of its journey.)

A practical guide to English grammar 74

But for a complete action in the past, we use the past simple.
The UFO went behind a cloud.
In these examples the past continuous means an action over a whole period.
The salesman was travelling from Monday to Friday.
We were watching for UFOs all night. We never went to sleep.
Here we could also use the past simple.

Period of time Complete action

He was travelling all week. He was very tired. He travelled all week. He drove a long way.

2 Past continuous and past simple

The period of a past continuous action can include a clock time.
I was walking home at quarter to eleven.
It can also include another action.
I was walking home when I saw the UFO.
Here the speaker sees one action as happening around another. The past continuous is the longer, background action (walking), and the past simple is the shorter, complete action (saw). The shorter action interrupted the longer one.
Here are some more examples.
Tim was washing his hair when the doorbell rang.
I had a sudden idea when/while/as I was waiting in a traffic queue.
The sun was shining when the campers woke.
When two actions both went on during the same period of time, we use the past continuous for both.
Tim was washing his hair while I was cleaning up the kitchen.
When one complete action followed another, we use the past simple for both.
Tim got up when the doorbell rang. (= The doorbell rang and then Tim got up.)

3 Past states

For a past state we normally use the past simple.
My grandmother loved this house.
I didn't know what to do.
The UFO appeared to be made of aluminum. It had a shape like a cigar.
With temporary states we can sometimes use the past continuous.