Bug: Diet calculator dates jump to 1900 in Internet Explorer

The \verb+get_selected_date+ JavaScript function ran afoul of another eccentricity of ``Internet Exploder'' (both 6 and 7). All reasonable browsers interpret the {\tt value} field of an {\tt Option} object within a selection field as the value which will be sent to the server when the value is selected, regardless of whether it was specified as the text within the {\tt option} tag or as a {\tt value=} attribute within the tag itself. But not Exploder---if you specify the value by the text within the tags, the {\tt value} property is blank; you have to use the {\tt text} property to obtain the value. This resulted in changes to the diet calculator causing the year within the start and end dates to warp back to 1900. I modified the function to use the {\tt text} property (which, thankfully, also works in Firefox and Opera. (Reported by Robert Ewing.)