Referring to time in the past

For, Since, During or Ago

For is used when we talk about a period of time
example:
I have worked for 3 hours

 Since is used when we talk about the beginning of the action
example:
I have worked since 8 o'clock

 Ago is used as a date
example:
I worked 2 days ago

 During is used with a noun
 For is used with a period of time
Compare:

He called her during her break and talked to her for more than twenty minutes.




Exercise 1: past time expressions
Exercise 2: choose the right words
Exercise 3: prepositionsof time – during, over, for, by, until