The words ‘since’ and ‘for’ are often confused by English language speakers. There is a simple rule to follow to differentiate between the usage of these twowords.
SINCE is used to talk about time from a specific period while FOR is used to talk abouta length of time.
I have been living in Delhi since 11002.
I have been living in Delhi for twenty years.
I have been studying since seven a.m. today.
I have been studying for eight hours.
My tutor has taught me since January this year.
My tutor has taught me for five months.