Compare an Active Directory user's non-replicated lastLogon attribute across domain controllers, and return the most recent value.

Get-ADUserLastLogon.ps1

# REQUIRED IMPORT
Import-Module ActiveDirectory
 
# FUNCTION
function Get-ADUserLastLogon {
    Param (
        [Parameter(Mandatory=$true]
        [string]$ADUser
    )

    $dcs = Get-ADDomainController -Filter {Name -like "*"}
    $user = Get-ADUser $ADUser
    $time = 0

    foreach($dc in $dcs) { 
        $hostname = $dc.HostName
        $currentUser = Get-ADUser $user.SamAccountName | Get-ADObject -Server $hostname -Properties lastLogon

        if ($currentUser.LastLogon -gt $time) {
            $time = $currentUser.LastLogon
        }
    }

    $dt = [DateTime]::FromFileTime($time)
    
    $output = [PSCustomObject]@{
        Name = $user.Name
        SamAccountName = $user.SamAccountName
        LastLogon = $dt
    }

    return $output
}

# EXAMPLE FUNCTION CALL
Get-ADUserLastLogon -ADUser dpiazza

# EXAMPLE OUTPUT
Name       SamAccountName LastLogon
----       -------------- ---------
Dan Piazza dpiazza        12/29/2020 9:29:59 AM