Get-Hotfix object installdate

I am a newbie and have completed the JumpStarts and working through the Learn Windows PowerShell 3 in a Month of Lunches and have run into something that has confused me with the Chapter 8 Lab. It wants me to select and sort by the Installed Date and when I look at the
members of the get-hotfix cmdlet, it shows ‘InstallDate’ but when you use it you don’t get a return. By just running get-hotfix, I notice the column ‘InstalledOn’. When I select InstalledOn instead of InstallDate I get the results I am expecting. My question is then, am I misunderstanding something?

PS C:> Get-HotFix | gm

TypeName: System.Management.ManagementObject#root\cimv2\Win32_QuickFixEngineering

Name MemberType Definition

PSComputerName AliasProperty PSComputerName = __SERVER
Caption Property string Caption {get;set;}
CSName Property string CSName {get;set;}
Description Property string Description {get;set;}
FixComments Property string FixComments {get;set;}
HotFixID Property string HotFixID {get;set;}
InstallDate Property string InstallDate {get;set;}
InstalledBy Property string InstalledBy {get;set;}
Name Property string Name {get;set;}

PS C:> Get-HotFix

Source Description HotFixID InstalledBy InstalledOn

CLTPF01UEW6 Update KB2899189_… NT AUTHORITY\SYSTEM 6/16/2014 12:00:00 AM

No, you’re not.

The InstallDate of the base object isn’t usually populated by the OS. The PowerShell team added InstalledOn, which is a ScriptProperty that digs into the object to get the date - so that you’ll have one.