Get approximate process launch time

$ssstudio = Start-Process -filepath "C:\Windows\system32\mmc.exe" -ArgumentList '"C:\Program Files\Citrix\Desktop Studio\Studio.msc" "C:\Program Files\Citrix\Desktop Studio\LaunchConsole.exe"' -PassThru

## change to whatever you need to match the title of the main window for the process you are measuring
while( $ssstudio.MainWindowTitle -notmatch 'Citrix Studio')
{
    Start-Sleep -Milliseconds 333 ## make smaller for greater accuracy but with increased CPU
    $ssstudio = Get-Process -id $ssstudio.Id -ErrorAction Stop
}
[void]$ssstudio.WaitForInputIdle()

[datetime]::Now - $ssstudio.StartTime