If ShowHeader is false, then list can be opened by hot keys. If ShowHeader is false and VisibleDayNames is None, then drop-down list is not supported.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Vista SP1 or later, Windows XP SP3, Windows Server 2008 (Server Core not supported), Windows Server 2008 R2 (Server Core supported with SP1 or later), Windows Server 2003 SP2