Date format hints are inaccurate for non-Chrome users

[briri]

The date hint on the search and report pages are invalid for non-Chrome users. The pages use the newish HTML5 date input type. Chrome provides a nice date picker widget but browsers like Firefox do not, and the resulting form submit does not work unless the date is entered as yyyy-mm-dd.

just update the text of the hint from dd/mm/yyyy to yyyy-mm-dd