Use for with a length of time: for five years, for two hours. Use since with the starting point: since 2021, since Monday, since I was a child. Both usually go with the Present Perfect when the situation continues now.
Same situation, two choices. Pick an example.
I've lived here for five years.
How long: the whole stretch of time, measured from end to end.
I've lived here since 2021.
From when: the moment it started, with the time running from there up to now.
| Rule | For | Since |
|---|---|---|
| Followed by | A period: five years, two hours, ages | A point: 2021, Monday, 10 o'clock, I was a child |
| Question | How long…? | Since when…? |
| Tenses | Any tense: I lived in Spain for two years. | Usually the perfect: I've lived here since 2021. |
| Example | She's worked here for a month. | She's worked here since May. |
I've had this phone _____ two years.
Paste an email or an essay. Clarigram marks the mistakes you actually make, shows the rule behind each one as a picture, and builds your practice from them.
Yes, for a finished period: I lived in Spain for two years (I don't live there now). Since almost always goes with the perfect.
When since is followed by a clause, that part is usually in the Past Simple: I've lived here since I moved in 2021.