Set this in the URL:
?startDate={!URLENCODE(TEXT(object.Start_date__c))}
and in the controller try this code:
Date startDate = Date.valueOf( EncodingUtil.urlDecode( ApexPages.currentPage().getParameters().get('startDate'), 'UTF-8') );
Set this in the URL:
?startDate={!URLENCODE(TEXT(object.Start_date__c))}
and in the controller try this code:
Date startDate = Date.valueOf( EncodingUtil.urlDecode( ApexPages.currentPage().getParameters().get('startDate'), 'UTF-8') );