I want to create a table which look like this:
+-----------------------------------------------------------+
|January 12th, 2012
As found in this answer you can set attributes for the entire table via colgroup and col. That way you are able to set individual attributes even for the (invisible single) cells inside the colspan in the first row.
In your example it would be:
January 12th 2011 this here is just for padding to make table wider
x
First item
Second item
Here's a fiddle