• while
  • when
  • as
  • all (the whole) day (morning / evening / night) yesterday
  • yesterday at 6 (7, 8, ...) o'clock / a.m. / p.m.
  • this time yesterday / this time last year (week / month)
Some other expressions that show that the action was happening at a particular time in the past:
  • when I first (did something)
  • the last time I (did something)
  • (from) the sounds / the smell … clear / obvious(ly)
  • in that photo
  • etc.
While you were playing football, I was reading a book.
When we were driving to work, we saw the accident.
As I was deciding what to do the bus arrived.
all (the whole) day (morning / evening / night) yesterday
They were playing computer games all day yesterday.
yesterday at … o'clock / a.m. / p.m.
It was raining yesterday at 7 p.m.
this time yesterday / last year (week / month)
This time last yearwas travelling by car across England.
when I first (did something)
When I first met him, he was studying drawing.
the last time I (did something)
The last time I went out with friends I was wearing my favourite jeans.
... the sounds / the smell clear / obvious(ly)
From the sounds it was clear that Susan was practising the violin.
There wasa strong smell and the sound of frying. Obviously, Mr Smith was cooking meat.
What was that noise? James was repairing his bike.
in that photo
We were playing together in that photo.