Is it possible to have two columns under the same header?

For example if I want to have “Date” as header/label, and under it two columns with “start date” and “end date”.

Perhaps I can do this by some sort of add-attribute colspan=2 to the header cell?

Also, how come when I set align:'center' in the colModel, the header is not aligned but only the cells? Can I also align the header?