Stop saying: “I have known David since five years.”
Say instead: “I have known David for five years.” · B1 · Prepositions
✗ Wrong
I have known David since five years.
✓ Correct
I have known David for five years.
Why?
Use for with a length of time: for five years, for two weeks, for an hour. Use since with a starting point: since 2020, since Monday, since last summer. Both work with the present perfect.
More examples
🎙️ REAL VOICES
The three correct examples below, in a real voice.
✗ She has worked here since three years.
✓ She has worked here for three years.
✗ We have lived in Boston for 2019.
✓ We have lived in Boston since 2019.
✗ He has been sick since two days.
✓ He has been sick for two days.
For counts the time; since names the starting line.