I have two textboxes in a form. The first textbox contains a calender. I would like to display after one year date in second text box based on the calender date selected in first text box. How to achieve this? I only know about getting the current textbox value but not how to put after one year date in second textbox.

PHP Code:
<td><input type="text" name="soname3" id="id1" size="15"
img src="../Image/cal.gif" id="" style="cursor: pointer;" onclick="javascript:NewCssCal('id1','MMddyyyy','dropdown',false,'12')" /></td>
td><input type="text" name="" id="id2" size="20"> </td