Witam,
dlaczego nie może być zdania np. I haven't been there since two years?
"When referring to time, "since" needs to refer to a paricular time."
"Since" musi odnosić się do konkretnej daty.
Łopatologicznie:
since - OD
for - PRZEZ
I have not been to US since 2010.
I have not been to US for two years.
Na przyszlosc - ang.pl dosyc fajna stronka.
http://www.ang.pl/gramatyka/czas/present_perfect/for_since
