The # symbol is used in Excel sheets for hyperlinks and dynamic arrays. It is also used in VBA for date definitions.

The # symbol can be used to surround a date you want to capture – see image below.

Unfortunately, the syntax between the # symbols is mm/dd/yyyy, which is the US date system, not the Australian date system.

You don’t have to use #. You can just enclose the date in quotation marks and Excel will convert it into a date. Then you can use the Australian date format of dd/mm/yy.