SharePoint Online - Document Library and List Date Error - Enter a date like this: 23/02/2012

Hello,

We have a few users suddenly having issues with applying / saving a date against document library metadata or in a SharePoint list from the normal datepicker in standard SharePoint "New" and "Edit" forms. These doc libs and lists have existed for a long time without any changes to them.

We are getting the following error - Enter a date like this: 23/02/2012

The dates on all the forms are defaulted to (for example) 2024-2-22. After choosing from the datepicker, it will also format it to 2024-2-22, which then comes up with the Enter a date like this: 23/02/2012 error.

It seems to be a problem with the datepicker. The date is accepted if you manually type in 22/2/2024.

Offline Client Availability is switched off on all locations and the regional settings are English (UK). Changing the date columns to "Friendly format" doesn't solve this either.

Any suggestions?

Thanks