This property returns false if the time slot falls on a non-working day, or falls outside the working hour range for a working day.
When the TimeScaleResolution of the associated DateTimeInterval is 'Week', 'Month', or 'Year', this property always returns true.
Target Platforms: Windows 10, Windows 8.1, Windows 8, Windows 7, Windows Server 2012, 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