The input field is not updated for the first click when using "onSelectDate"

[mb13]

I want to allow only future times since the actual time. I have the following code:

        var now='2015-10-21 16:00';
        .
        .
        .
        onSelectDate:function(ct,$i){
            var temp = ct.getFullYear() + '-' + (ct.getMonth()+1) + '-' + ct.getDate();
            if (now.substr(0,10) != temp) {
                this.setOptions({
                    minTime:'00:00'
                });
            } else { // the day is today
                this.setOptions({
                    minTime:now.substr(11,5) // set today's time
                });
            }
        }

But on the first selection of the day, the input-text is not updated. It is updated if I click the second time. And also sometimes after a certain number of day selection the datetimepicker disappears. How to get rid of these issues?