Add a new attribute called "showApplyButton" (boolean, default=false) to the component. When "showApplyButton=false" (default), the popup behavior is the same as it is now such that clicking anywhere off the popup, or clicking the "X" button will both close the popup and apply the selected date-time value. Similarly, when "showApplyButton=true" a button appears at the bottom of the popup with the "Apply" label (from the resources file, of course). When the user clicks the apply button, it closes the popup and applies the selected value (the same action that clicking the "X" button to hide the popup, or clicking anywhere off the popup does now). However, when "showApplyButton=true" the popup should not close automatically when the user clicks off of it, and closing it by clicking the "X" icon should close the popup and not apply the edited value (cancels the edits).
  
Note that the behaviors exhibited by these additional component modalities must be described adequately in the component documentation.