Display Alert

while saving an event Start date must be lesser than End Date , then only the event should be saved .
suppose i given the Start date is 10-08-2010 && End Date is 01-08-2010 like this , i need to display an alert that check the End Date .

Logic of scheduler will fix end date automatically, but setting it as start_date + time_step

You can use onEventSave handler to check values of start and end time, and show any kind of custom message if values are not valid.