Get Uptime for list of computers with basic errorhandling. It's processed in parallel.

Get-UptimeParallel.ps1

Function Get-Uptime {
    <#
    .Synopsis
    Get computer uptime.
    .Description
    This command will query the Win32_OperatingSystem class using Get-CimInstance and write an uptime object to the pipeline.
    The function is calling workflow to parallely process all inputs to save some time.
    .Parameter Computername
    The name of the computer(s) to query. This parameter has an alias of CN. The Input can be piped.

    .Example
    PS C:\> get-myuptime pc1,pc2,pc3
 
    ComputerName LastBootUpTime      Days Hours Minutes Seconds TotalDays
    ------------ --------------      ---- ----- ------- ------- ---------
    PC1          11.12.2014 0:27:07    49     8      35      39 49,36    
    PC2          27.12.2014 17:58:36   32    15       4      10 32,63    
    PC3          Not Accessible                                          
 
    Formatted results for multiple computers. You can also pipe computer names into this command.

    .Notes
    Last Updated: January 27, 2015
    Version     : 1.0
  
    .Link
    #>
 
    [cmdletbinding()]
    Param(
        [Parameter(Position=0,ValueFromPipeline,ValueFromPipelineByPropertyName)]
        [ValidateNotNullorEmpty()]
        [Alias("cn","name")]
        [String[]]$ComputerName,

        [System.Management.Automation.CredentialAttribute()]$credential

    )
    
    Workflow Get-HostUptime{ 
        Param(
            [String[]]$ComputerName, 
            [System.Management.Automation.CredentialAttribute()]$credential
        )
            Foreach -parallel ($computer in $computername){
                sequence{
                    #InlineScript {
                        Try {$wmi = gwmi Win32_OperatingSystem -PSComputerName $Computer -PSCredential $credential -ErrorAction Stop
                            $LBTime = [System.Management.ManagementDateTimeconverter]::ToDateTime($wmi.LastBootUpTime)
                            $uptime = [DateTime]::Now - $LBTime
                            $Obj = [PSCustomObject] @{
                                ComputerName = $Computer.ToUpper()
                                LastBootUpTime  = $LBTime
                                Days = $uptime.Days
                                Hours = $uptime.Hours
                                Minutes = $uptime.Minutes
                                Seconds = $uptime.Seconds
                                TotalDays = $uptime.totaldays
                            }
                        } #try
                        Catch {
                            $Obj = [PSCustomObject] @{
                                ComputerName = $Computer.ToUpper()
                                LastBootUpTime  = "Not Accessible"
                            }
                        } # catch
                        $Obj 
                    #} # InlineScript
                } # Sequence
            } # ForEach
    } #end workflow
    

    $CurrentPath = Get-Location # to achieve no problems when workflow is called from custom mapped PSDrive
    Set-Location $env:SystemRoot # cange location before workflow
    if ($Credential) {Get-HostUptime -ComputerName $ComputerName -Credential $credential | sort-object -Property LastBootUpTime -Descending | Select-Object ComputerName,LastBootUpTime,Days,Hours,Minutes,Seconds, @{Name="TotalDays";Expression={"{0:N2}" -f $_.TotalDays}} | ft -autosize }
    else {Get-HostUptime -ComputerName $ComputerName | sort-object -Property LastBootUpTime -Descending | Select-Object ComputerName,LastBootUpTime,Days,Hours,Minutes,Seconds, @{Name="TotalDays";Expression={"{0:N2}" -f $_.TotalDays}} | ft -autosize }
    Set-Location $CurrentPath #return location to original path


} #end function uptime