Длительное время

to be + глагол+ing
is
am
are
was
shall / will be
were
Образование

Употребляется, когда действие происходит в определенный момент или период времени:
сейчас (now, at the moment)
I am reading a book now.
He is playing a computer game now.
They are talking over the telephone at the moment.
В 2 часа вчера, в 5 часов в прошлое воскресенье, c 2 до 3 вчера:
She was shopping at 2 o’clock yesterday.
We were playing tennis at 5’clock on Sunday.
They were swimming from 2 till 3 yesterday.
My brother was watching TV all day long yesterday.
My mother was cooking when I came home.

Длительное время
не употребляется:
с глаголами умственной деятельности: to think, to know, to understand, to remember, to forget и т.д.
с глаголами чувственного восприятия: to see, to hear, to feel, to taste, to smell
с глаголами, обозначающими чувства и эмоции: to love, to like, to hate и т.д.
c глаголами, обозначающими обладание: to have, to own, to belong