Function Get-Uptime {
      Param([string]$server)
      Begin {
           function Uptime {
                param([string]$srv)
                $os = Get-WmiObject Win32_OperatingSystem -ComputerName $srv
                $uptime = $os.LastBootUpTime
                return $uptime
           } 
           function ConvertDate {
                 param([string]$date)
                 $year = $date.substring(0,4)
                 $Month = $date.Substring(4,2)
                 $Day = $date.Substring(6,2)
                 $hour = $date.Substring(8,2)
                 $min = $date.Substring(10,2)
                 $sec = $date.Substring(12,2)
                 $RebootTime = new-Object System.DateTime($year,$month,$day,$hour,$min,$sec)
                 $now = [System.DateTime]::Now
                 $uptime = $now.Subtract($RebootTime)
                 Write-Host "==> Uptime: " -NoNewLine
                 Write-Host "$($uptime.days)" -NoNewLine -ForeGroundColor Green
                 Write-Host " days, " -NoNewLine
                 Write-Host "$($uptime.Hours)" -NoNewLine -ForeGroundColor Green
                 Write-Host " hours, " -NoNewLine
                 Write-Host "$($uptime.Minutes)" -NoNewLine -ForeGroundColor Green
                 Write-Host " minutes, " -NoNewLine
                 Write-Host "$($uptime.seconds)" -NoNewLine -ForeGroundColor Green
                 Write-Host " seconds, "
            } 
                 Write-Host 
                 $process = @()
       }
       Process {
              if($_){
                    if($_.ServerName ){
                             $process += $_.ServerName
                     }
                    else{
                             $process += $_
                    }
              }
        }
       End {
              if($Server){
                     $process += $server
              }
              foreach ($Server in $process){
                        $result = uptime $server
                        Write-Host "Uptime for Server [" -NoNewline
                        Write-Host $server -NoNewline -foregroundcolor Cyan
                        Write-Host "]"
                        ConvertDate $result
                        Write-Host
               }
               Write-Host
         }
}

PS C:\> Get-Uptime monserveur