SSRS 2012 SP2, Native / Report Manager, non-IE browsers show date parameters in US format MM/DD/YYYY, ignoring locale settings

I have a server running SSRS 2012 SP2, in Native / Report Manager mode. The server, reports, desktop etc are all set to en-AU.

Using IE, date parameters show as expected in DD/MM/YYYY format.  However using Chrome or Firefox, they show in US format MM/DD/YYYY.

Does anyone know how to fix this?