Your timeWheels attribute is incoreect, change it to this:
$('#datetime-start, #datetime-end').mobiscroll().datetime({
minDate: new Date(now.getFullYear(), now.getMonth(), now.getDate()),
display: 'modal',
animate: 'pop',
mode: 'mixed',
// 2013-03-15 11:26:17
dateFormat: 'yy-mm-dd',
timeFormat: 'HH:ii:ss',
timeWheels: 'HHii'
});
So change this:
timeWheels: 'hhii'
to this:
timeWheels: 'HHii'