Get-RealLogonDate

function Get-RealLogonDate {
    [CmdletBinding()]
    Param (
        [Parameter(Mandatory = $true,
                   Position = 0)]
        [String]$sAMAccountName,

        [Parameter(Mandatory = $true,
                   Position = 1)]
        [String]$Domain
    )

    # Build a domain object so we can get a list of domain controllers
    try {
        $domainContext = New-Object System.DirectoryServices.ActiveDirectory.DirectoryContext('Domain', $Domain)
        $domainInfo = [DirectoryServices.ActiveDirectory.Domain]::GetDomain($domainContext)
    }
    catch {
        throw ('Unable to connect to {0}: {1}' -f $Domain, $_.exception.message)
    }

    # Pull out all of the dc's in the domain.
    [array]$dcList = $domainInfo.DomainControllers | foreach { $_.name }
    Write-Verbose -Message ('[GetRealLogonDate] Found {0} DCs in {1}' -f $dcList.count, $Domain)

    # Define a script block which we'll use to feed into a job.
    $queryBlock = {
        Param (
            [Parameter(Mandatory = $true,
                       Position = 0)]
            [String]$sAMAccountName,

            [Parameter(Mandatory = $true,
                       Position = 1)]
            [String]$ComputerName
        )

        # Search the domain controller for the user in question
        $searcher = new-object System.DirectoryServices.DirectorySearcher([ADSI]"LDAP://$ComputerName")
        $searcher.filter = "(&(objectClass=User)(lastlogon=*)(sAMAccountName=$sAMAccountName))"
        [void]$searcher.PropertiesToLoad.Add('lastlogon')
        try {
            $userObj = $searcher.FindOne()
        }
        catch {
            return $null
        }

        # Write out a match to include the DC, their name, and the last long as a number (this is important, we don't want to convert it yet)
        Write-Output $(New-Object -TypeName PSObject -Property @{ DC = $ComputerName; sAMAccountName = $sAMAccountName; LastLogon = [int64]$($userObj.Properties.lastlogon | Out-String).trim() })
    }

    # Go through each DC in the list and query for the user account.
    $queryQueue = New-Object System.Collections.ArrayList
    for ($i = 0; $i -lt $dcList.count; $i++) {
        Write-Verbose ('[GetRealLogonDate] Running jobs: {0}' -f (Get-Job -State Running).Count)
        # If there are more than 10 jobs running wait until they finish.
        While ((Get-Job -State Running).Count -ge 10) {
            Start-Sleep -Seconds 3
        }

        Write-Verbose ('[GetRealLogonDate] Starting job for {0}' -f $dcList[$i])
        Start-Job -Name $dcList[$i] -ScriptBlock $queryBlock -ArgumentList $sAMAccountName, $dcList[$i] | Out-Null

        # Get any completed jobs and add them to our query queue.
        Get-Job -State Completed | Where { $_.Name -like "*.$Domain.*" } | Receive-Job -Wait -AutoRemoveJob | foreach { [void]$queryQueue.Add($_) }
    }

    # Look for and get any pending jobs and then receive them as well.
    Write-Verbose ('[GetRealLogonDate] Waiting for running jobs to finish')
    Get-Job | Wait-Job | Receive-Job -Wait -AutoRemoveJob | foreach { [void]$queryQueue.Add($_) }

    # Init log to 0 and then go through each result we got and compare to the value of log (starting with 0).
    # Since the value for lastlogon is an integer we can easily compare to see which number is greater.  The goal
    # is to get the number which is highest and then convert that to a datetime object.
    $log = 0
    for ($q = 0; $q -lt $queryQueue.count; $q++) {
        if ($queryQueue[$q].LastLogon -like $null) { continue }
        if ($queryQueue[$q].LastLogon -gt $log) { $log = $queryQueue[$q].LastLogon }
    }

    # Return the value in $log and convert to a datetime object.
    Write-Output $([datetime]::FromFileTime($log))
}