Prepositions

For and since

We use for and since to say how long.

For refers to a period of time.

• I've worked in this office for three years.

Since refers to a point in time.

• I've worked in this office since 2008.

For and since are often used with the present perfect to talk about actions that began in the past and continue now.

• I've lived in this apartment for three years.
  NOT: I live in this apartment for three years.

• I've lived in this city since last January.
  NOT: I live in this city since last January.