$.fn.attachDatepickerInputKeys = function(callback) {
    if (this.length < 1) return this;

    this.keydown(function(e) {
        var j = jQuery(this);
        var di = $.datepicker._getInst(this);
        if (!di)
            return;

        $.datepicker._setDateFromField(di);  // force update first

        var d = j.datepicker('getDate');
        if (!d)
            return true;

        var month = d.getMonth();
        var year = d.getFullYear();
        var day = d.getDate();

        switch (e.keyCode) {
            case 84: // [T]oday
                d = new Date(); break;
            case 109: case 189:
                d = new Date(year, month, day - 1); break;
            case 107: case 187:
                d = new Date(year, month, day + 1); break;
            case 77: //M
                d = new Date(year, month - 1, day); break;
            case 72: //H
                d = new Date(year, month + 1, day); break;
            default:
                return true;
        }
        
        j.datepicker('setDate', d);
        if (callback)
            callback(this);
        return false;
    });
    return this;
}


$.maxZIndex = $.fn.maxZIndex = function(opt) {
    /// <summary>
    /// Returns the max zOrder in the document (no parameter)
    /// Sets max zOrder by passing a non-zero number
    /// which gets added to the highest zOrder.
    /// </summary>    
    /// <param name="opt" type="object">
    /// inc: increment value, 
    /// group: selector for zIndex elements to find max for
    /// </param>
    /// <returns type="jQuery" />
    var def = { inc: 10, group: "*" };
    $.extend(def, opt);
    var zmax = 0;
    $(def.group).each(function() {
        var cur = parseInt($(this).css('z-index'));
        zmax = cur > zmax ? cur : zmax;
    });
    if (!this.jquery)
        return zmax;

    return this.each(function() {
        zmax += def.inc;
        $(this).css("z-index", zmax);
    });
}