CiviReport Participant Sort by Event Start Date
Yeah, it's pretty silly that event start date isn't available as a header.  It's actually a really small change in the code, but it does require editing the code to add the field as an sorting option.

I made a change that will hopefully be included in the next 4.6 release, but you can add it by editing the appropriate file.  In your CiviCRM codebase (found at sites/all/modules/civicrm in Drupal, administrator/components/com_civicrm/civicrm in Joomla, or wp-content/plugins/civicrm/civicrm in WordPress), edit the file at CRM/Report/Form/Event/ParticipantListing.php to apply the changes you see here: https://github.com/civicrm/civicrm-core/pull/7221/files after line 299.