CalendarExtender getting overlapped when rendered

Unfortunately there is no Z-Index attribute to the CalendarExtender, unless you want to write an entire style for the calendar, which I don't want to do. However, you can extend the default style by adding the following to your CSS file:

.ajax__calendar_container { z-index : 1000 ; } 

If you aren't using a CSS file, you can also add this into the head section of your page:

<style type="text/css"> 
   .ajax__calendar_container { z-index : 1000 ; } 
</style>

 

and that should do the trick. It worked for me.