Since est un indicateur de début qui permet de calculer la durée. Il est suivi d’une date ou d’un moment précis.
For exprime la durée d’un évènement, mais ne donne pas de repères temporels.
Enfin, during donne un repère temporel, mais pas une durée précise.
Les exemples :
Since : He has lived in Boston since he arrived in the USA.
He is always late. I have already waited for him since 2 PM and he hasn’t come yet.
For : He has worked with us for three year.
If you want people to understand you when you speak Spanish, you need to study for a few months.
During : She worked in London during the summer months in 2010.
It was so boring I fell asleep during the film.