Why doesn't the time-showing script work with os and RunService?

I'm trying to make a simple clock on-screen in real time using os and RunService. But it doesn't work. I have no idea on what *t means. Error:

os.date's first argument must be either *t or !*t

Code:

game:GetService("RunService").RenderStepped:Connect(function()
	local thing = script.Parent.TextLabel.Text
	script.Parent.TextLabel.Text = os.date(thing*t,os.time())
end)

Thanks, b_mni.