This may not be the best or most up to date solution but it may suit your needs?
Create a parent list with the following codes defined ...
1-Holidays
2-Salary
3-Holidays
4-Salary
Create a grid question with the columns using the above mentioned parent list. The rows will use a single row blank list.
Set the grid direction to rows.
Set your input type - radio button / check boxes / numeric / etc.
Pop this JavaScript into the footer of your grid question ...
<script>
$(document).ready(function()
{
row_html = "<tr></td><td align='center' colspan='2'>Year</td><td align='center' colspan='2'>Month</td></tr>";
$(".column_header_row").before(row_html);
});
</script>
Good luck.