Extract spesific date in string regex

I have following string

Документ подписан аналогом собственноручной подписи Клиента (простой электронной подписью): [349522252]
[01.12.2019][8605]
Дата подписания: 01.12.2019

I need to extract date so result should be 01.12.2019. I fugured out how to extract something between [...]

(?<=\[)(.*?)(?=\])

but it’s captured wrong

>Solution :

You can use

(?<=\[)\d{1,2}\.\d{1,2}\.\d{2}(?:\d{2})?(?=\])

See the regex demo.

Details:

• (?<=\[) – a positive lookbehind that matches a location that is immediately preceded with a [ char
  –\d{1,2} – one or two digits
• \. – a dot
• \d{1,2}\. – one or two digits and a dot
• \d{2}(?:\d{2})? – two or four digits
• (?=\]) – a positive lookahead that matches a location that is immediately preceded with a ] char.