Set custom time on select box change event using jquery

Hello All,
I am using dhtmlx scheduler.I want to set custom time duration on select box change event using jquery in lightbox.And i want to hide the time section.If i am hiding time i am getting error while saving that “Uncaught error for a.getDate”.
I just want to select a start date from custom filed and i will set a time duration so that it will automatically map to that specific time.