“When’s your birthday? 23/10. When are we going to Mum’s? 19-29/11. When do you go back into therapy? 8/12.”

As it could be written in English in Britain, Australia etc.

23/10 is pronounced "23rd of October" or (usually) "23rd'f October" or "23rd'f the 10th".

The range is "19th to 29th of November" or "... of the 11th".

The pronunciation "second of the second twenty-twenty" is usually used when the listener is writing, typing or confirming the date in figures.