They have been together since the beginning of their relationship.
since childhood
Frequency:
60
%
They have known each other since childhood.
since last year
Frequency:
50
%
She has been working at the company since last year.
since yesterday
Frequency:
45
%
I have been feeling unwell since yesterday.
Idiomatic Expressions for since
Phrase: Since the dawn of time
Meaning: For as long as anyone can remember; since the beginning of history
Usage: Humans have been fascinated by the stars since the dawn of time.