Summary: Use Windows PowerShell to find your system uptime.
How can I use Windows PowerShell to easily find how long my computer has been running?
Use the Get-Date cmdlet to return the current date and time, and then subtract the value
of the LastBootUpTime property that comes from the Win32_OperatingSystem, for example:
(get-date) - (gcim Win32_OperatingSystem).LastBootUpTime
Note GCIM is an alias for Get-CimInstance.