We use '~' + noun to say when something happens (not how long):
- ~ the film (I fell asleep ~ the film.)
- ~ our holiday (We met a lot of interesting people ~ our holiday.)
- ~ the night (The ground is wet. It must have rained ~ the night.)
Wecan not use '~' + subject + verb.
For example, we cannot say: *I fell asleep ~ I was watching television.