How to find out Windows Uptime?

Using PowerShell:

powershell ((Get-Date) - (gcim Win32_OperatingSystem).LastBootUptime).ToString('g')

powershell ((Get-Date) - ([wmi]'').ConvertToDateTime((Get-WmiObject win32_operatingsystem).LastBootUpTime)).ToString("dd' days 'hh\:mm\:ss")

Also, I cobbled together this little script that looks like the Linux uptime cmd. It’s embedded in a batch file so for ease of running (https://blogs.msdn.microsoft.com/jaybaz_ms/2007/04/26/powershell-polyglot/ for more info). Gist: https://git.io/v5tx0.

@PowerShell -ExecutionPolicy RemoteSigned -Command Invoke-Expression $('$args=@(^&{$args} %*);'+[String]::Join(';',(Get-Content -LiteralPath '%~f0') -notmatch '^^@PowerShell.*EOF$')) & goto :EOF

$d = Get-Date
$upTime = (($d) - ([wmi]'').ConvertToDateTime((Get-WmiObject win32_operatingsystem).LastBootUpTime)).ToString("d' days,  'h\:mm")
$ActiveUsers = @()
foreach($User in (Get-WmiObject Win32_LoggedOnUser).Antecedent) { $ActiveUsers += $User.Substring($User.LastIndexOf('=') + 2, $User.Length - $User.LastIndexOf('=') -3) }
$UserText = "$($ActiveUsers.Count) user"
if ( $ActiveUsers.Count -gt 1 ) { $UserText += "s" }
$TotalProcTime = (Get-Counter "\Processor(_total)\% Processor Time") | foreach {$_.CounterSamples[0].CookedValue}

Write-Host -NoNewLine (" {0}, up {1},  {2},  total proctime: {3}%" -f $d.toString("HH:mm:ss"), $upTime, $UserText, [math]::Round($TotalProcTime,2))

Output looks like this:

C:\Users\silver>uptime
 14:45:41, up 5 days,  20:15,  3 users,  total proctime: 2,26%

GUI (Windows 10):

Task Manager (taskmgr) > More details > Performance tab > CPU

Boot Time:

net stats <workstation/server>
systeminfo | findstr "System Boot Time"