hi team,

the dangerous part is

Code:
add( String interval, Number value, Object value) : Void
which has not the correct order. it is

Code:
add(Object date, String interval, Number value) : Void
example 2 and 3 also point to the ext 3 version of a changed javascript date prototype:

Code:
// Basic usage:
var dt = Ext.Date.add(new Date('10/29/2006'), Ext.Date.DAY, 5);
console.log(dt); //returns 'Fri Nov 03 2006 00:00:00'

// Negative values will be subtracted:
var dt2 = new Date('10/1/2006').add(Ext.Date.DAY, -5);
console.log(dt2); //returns 'Tue Sep 26 2006 00:00:00'

// You can even chain several calls together in one line:
var dt3 = new Date('10/1/2006').add(Ext.Date.DAY, 5).add(Ext.Date.HOUR, 8).add(Ext.Date.MINUTE, -30);
console.log(dt3); //returns 'Fri Oct 06 2006 07:30:00'

best regards
tobiu