SINCE
*
FOR

WORD	USE WITH PERFECT TENSES	EXAMPLE 1	EXAMPLE 2
SINCE	we use since when we want to say that we were doing something (and we're still doing it) from a certain point in the past	since May since 1976 since yesterday	*I have lived in New York since* 1990.**( it means that I moved to NY in 1990 and I still live there )
FOR	we use for when we want to say that we were doing something in a certain time ago and probably we're still doing it	for three days for years for seven hours	*She has learnt German for* two months.** ( it means that she started to learn German two months ago and she's still learning German, probably not at the moment, but around now)

SINCE* FOR