Q:

It's been called a twitter presidency

How can we write the structure "it's been called". I don't understand. 
Written by the Hindu Editorial on Saturday 

A:

“It's been called a Twitter presidency”
The Times of India 
It (refers to the presidency) has been called (is written in the present perfect passive voice). In the active voice the sentence would be:
“Historians/journalists/lawyers/ambassadors (whoever) have called the last four years ‘The Twitter presidency’”.

