Meaning of the word "Before you know it" in English

What does "Before you know it" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

Before you know it

US /bɪˈfɔr ju noʊ ɪt/
UK /bɪˈfɔː ju nəʊ ɪt/

Idiom

very quickly; sooner than you expect

Example:
The children will be grown up before you know it.
The holidays will be here before you know it.