Thanks for your post.
We also unable to set ‘Checked’ property, it could be a bug in this property.
Are you using Formativ 1.5 or 2.0? If you are using Formativ 2.0 or onwards then you can use the dynamic visual forms designer. You can create a new applet, on the editor toolbar in Formativ, press the ‘Forms’ button. Create a new form from the dialog shown. The visual forms designer appears, drag and drop components from the palette onto the form. There are two types of date time controls available in Formativ 2.0: DateTimePicker (Win32 tab), RzDateTimeEdit (Enhanced tab).
Documentation for Forms Designer and Components: http://www.advansyscorp.com/forums/topic/3971028821/
Hope this helps.