how to change daytime again?

I know it seems confusing, but i'm trying to make it after 180 seconds it changes back to noon, can anyone help?

local minutes = 0
local hours = 0

while true do
	game.Lighting.TimeOfDay = hours.."20:00:00"..minutes
--what is the changed time
	wait(script.WaitToAdd.Value)
	minutes = minutes + script.AddAmount.Value
	if minutes >= 60 then
		hours = hours + 1
		minutes = 0
		if hours >= 24 then
			hours = 0
		end
	end
end
--i wanted to change it back to 12:00:00.

Is this what you're trying to do?

local RunService = game:GetService("RunService")
local hb = 1/60

local length = 360 -- Set this to how long, in seconds, you want the whole day to last for (from midnight back to midnight again.)

while true do
	game.Lighting:SetMinutesAfterMidnight(game.Lighting:GetMinutesAfterMidnight() + ((1440/length) * hb))
	hb = RunService.Heartbeat:Wait()
end