AD Logon Hours
http://msdn.microsoft.com/en-us/library/ms180833(vs.80).aspx
PS C:\> [byte[]]$hours = @(0,0,0,0,255,3,0,255,3,0,255,3,0,255,3,0,255,3,0,0,0)
PS C:\> # create a hashtable to update the logon hours and a description
PS C:\> $replaceHashTable = New-Object HashTable
PS C:\> $replaceHashTable.Add("logonHours", $hours)
PS C:\> $replaceHashTable.Add("description", "Logon M-F from 8:00 AM to 6:00 PM")
PS C:\> Set-ADUser "StevieWonder" -Replace $replaceHashTable
objUser.Properties["msNPAllowDialin"].Add(true);