I've been up for days!!

When was that machine last rebooted?

function Get-Uptime {

param([string]$computer = $env:computername)

$computer = $computer.toupper()

if (Test-Connection $computer -Count 1 -ea silentlycontinue) {

    $WMITimeString = (gwmi -Query "Select lastbootuptime from win32_operatingsystem" -computer $computer).lastbootuptime

    $bootTime = ([wmi]'').ConvertToDateTime($WMITimeString)

    $formattedTime = (Get-Date $bootTime).datetime

    Write-Host -fore green -Background black "Computer $computer has been up since:`n`n`t $formattedTime"

    }else {Write-Host -fore red -Background black "Computer $computer is not online."}

}

The script will check the local machine if no parameter is specified.