jQuery DateTimePicker is subtracting one hour on input blur
Here's an open issue on project GitHub repository: Format "m/d/Y h:i a" changes hour onBlur #596 https://github.com/xdan/datetimepicker/issues/596
btw, there is a workaround
$('#start').datetimepicker({
format:"Y-m-d H:i A",
validateOnBlur: false,
step:15
});