Два предлога – FOR/SINCE

We use for + period of time

(two hours, six weeks etc.):

I’ve been waiting for two hours.

Two hours ago                                  now

two hours       a long time        a week

20 minutes       six months           ages

five days             50 years         years

We use since + the start of a period

(8 o’clock, Monday, 1999 etc.):

I’ve been waiting since 8 o’clock.

8 o’clock                                 now

8 o’clock            April               lunchtime

Monday             1985                we arrived

12 May          Christmas            I got up