For compulsive bookers over 12 months ahead [Sometimes rates are lower than they are a month later] there is a peculiarity in the new calendar on hyatt.com.
If you try to book using the calendar it only works for 364 or 365 days ahead.So on May 1, you can only book until April 30 2011.
However if you manually insert later days in May you can find results for those dates. That opens up the drop down calendar that is open for all of May 2011.