 <p>How about something like this -</p> <pre><code>$cal = New-Object -Type PsObject -Prop @{ Year = 2013 Events = @() } $event = New-Object -Type PsObject -Prop @{ Date = [DateTime] "2013-02-14" Name = "Valentines Day" } $cal.Events += $event </code></pre> <p>If you have a predefined calendar objects which doesn't have a property to store events you can use <code>Add-Member</code> to attach a new property and store an array in there.</p>