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