Custom date attribute

Hello -
I am trying to change the format of dates in filenames (e.g. NHS Digital CareCERT Security Advisory 22 01 2021.pdf). Whilst I am succeeding for dates like 01.02.2019 using automatic date detection, automatic detection seems not to work for dates like 01 02 2019 i.e. with space delimiters. Neither, it seems, do custom formats such as 31 12 1999 or 31…12…1999: see screenshots at http://chrisbunch.uk/docs/S1.png, http://chrisbunch.uk/docs/S2.png and http://chrisbunch.uk/docs/S3.png.
What am I doing wrong?
Chris
I am trying to change the format of dates in filenames (e.g. NHS Digital CareCERT Security Advisory 22 01 2021.pdf). Whilst I am succeeding for dates like 01.02.2019 using automatic date detection, automatic detection seems not to work for dates like 01 02 2019 i.e. with space delimiters. Neither, it seems, do custom formats such as 31 12 1999 or 31…12…1999: see screenshots at http://chrisbunch.uk/docs/S1.png, http://chrisbunch.uk/docs/S2.png and http://chrisbunch.uk/docs/S3.png.
What am I doing wrong?
Chris