Thanks for letting us know. Just tried and am getting the same error. The page is loading content dynamically from another source... We'll look into this and see if we can get it working on this page
curl "https://www.keepandshare.com/calendar/fns_asynch_api.php?r=0... --data "action=getrange&i=1940971&from=2013-12-26&to=2014-02-06"