Are you talking about uploading a flattened panorama to Facebook?
If so, I believe that Facebook removes all metadata from all photos uploaded to Facebook.
Are you talking about sharing a link to an interactive panorama which you've uploaded to your account here on Photosynth.net?
If so, the date that you took the panorama won't be displayed, but the date that you uploaded the panorama (or photosynth, if you've used the Windows app) will be displayed below the viewer. You could get around this by editing the URL from view.aspx to embed.aspx if you like which would hide the comments, author information, etc. and only show the photography.
Here's an example:
Normal link: http://photosynth.net/view.aspx?cid=ccf78d3c-9813-4741-8945-0afb06ed5073
Embed link: http://photosynth.net/embed.aspx?cid=ccf78d3c-9813-4741-8945-0afb06ed5073
Hopefully that will solve your dilemma.
Your fellow photosynther + panner,