How to check the system up time

function Get-SystemUptime 
{
   $os = Get-WmiObject win32_operatingsystem
   $uptime = (Get-Date) - ($os.ConvertToDateTime($os.lastbootuptime))
   Write-Output "Uptime: $($Uptime.Days) days, $($Uptime.Hours) hours, $($Uptime.Minutes) minutes"
}