Add another valid date format

Hi
Anyone have any luck with adding another valid date format? Client has a requirement to pass dates to a webhook with YYYYMMDD format.
Changing the default date format in the global settings to Ymd returns an error on the form to enter a valid date, although the date displays in that format.
Have searched everywhere for an answer. The webhook cannot take YYYY.MM.DD as a format.

Would be ideal to add that accepted format to the global date dropdown?