For and Since with Present Perfect Tense

We often use for and since with perfect tenses:

for since
a period of time a point in past time
- - - - - - - - - - - - - • - - - - - - - - - -
20 minutes 6.15pm
three days Monday
6 months January
4 years 1994
2 centuries 1800
a long time I left school
ever the beginning of time
etc etc

Look at these example sentences using for and since with the Present Perfect tense:

For can be used with all tenses. Since is usually used with perfect tenses only.