I 've known her since 2011
My father has worked in this office since last year
Olga has read that book since morning
They have done their homework since two o'clock
Tom has riden the bike since morning.
Olga has already slept for nine hours
I've had this red pencil-box for two years
My Mum has kept the diet for three weeks
His friends have stayed in that hotel for eight days
Wind has blown for five hours