We use ‘since’ in front of a finished point in time in the past. For example:
since last Tuesday
We normally use ‘since’ with the present perfect to describe an action or situation that began in the past and continues in the present.
We’ve been married since 1995.
I’ve worked here since 2008.
She’s lived in New York since 2014.
They’ve been here since 4pm.
You’ve had that cold since last month!
He’s taken part in four conference calls since 9:30.
We can also use ‘since’ with a past action (which is similar to referring to a finished time). In this case it is often preceded by ‘ever’. For example:
They’ve argued ever since they came back from their honeymoon.
Since I met Astrid I’ve tried to learn German.
It’s been ages since we went to the sea on holiday.
You’ve been complaining ever since you arrived!
He’s had a car since he started working.
It hasn’t rained since we reopened the school.
We use ‘for’ with a period of time. For example:
for two years
for eight hours
for a long time
We can also use ‘for’ with the present perfect to describe an action that started in the past and continues in the present.
We’ve been married for 22 years.
I’ve had this car for three months.
She’s worked there for ten years.
They’ve lived here for 40 years.
He’s played with that toy for hours.
It hasn’t snowed for years.
But we can also use ‘for’ with other verb tenses. For example:
We’re staying in the mountains for 10 days. (present continuous)
She lived in Japan for three years. (simple past)
I’ll be at reception for a few minutes. (simple future)
They normally study for an hour then have a break. (present simple)
In December we’ll have been married for 25 years! (future perfect)