You can attach several handlers to the same event and detach them using two respective methods:
attachEvent() - to attach event
var myEvent = myCalendar.attachEvent("onClick", function (){
//event handler code
})
detachEvent() - to detach event
myCalendar.detachEvent(myEvent);
onBeforeChange - fires before a user starts to change month, year or time in selector.
onClick - fires after a user selects date.
onChange - fires when a user changes month, year or time in selector.