ASP Ajax Calendar Extender和显示时间

I am using the Ajax Control Toolkit Calendar Extender control. In some fields though I want to display the time along with the date. I have tried just setting the Format to "dd/MM/yyyy hh:mm:ss" but the time section gets wiped off. If the user wants to change the time section they can do it manually, the calendar drop down is only used for changing the date part. I am using the Ajax Control Toolkit Calendar Ex