global countdown timer help please?

so ive been trying to make a global countdown timer that is in sync with all players, and i dont know why but it just doesnt work

-- server script
local event = Instance.new("RemoteEvent")
event.Parent = game.Workspace
event.Name = "UpdateText"
game.Workspace.UpdateText:FireAllClients()

-- local script
local client = game.Players.LocalPlayer
local playergui = client.PlayerGui
local event = game.Workspace:FindFirstChild("UpdateText")
event.OnClientEvent:connect(function()
for i=850,0,-1 do 
	wait(1)
    playergui.ScreenGui.Frame.TextLabel.Text = ("Time left: "..i)
end
end)

I would send the timer on the server rather than the client

Server

local event = game:GetService("ReplicatedStorage"):FindFirstChild("UpdateText")
-- I would put the event in ReplicatedStorage so it's filtering enabled
local timeLength = 850

for i=timeLength,0,-1 do
	wait(1)
	event:FireAllClients(i)
end

Client

local event = game:GetService("ReplicatedStorage"):FindFirstChild("UpdateText")
-- I would put the event in ReplicatedStorage so it's filtering enabled
local  client = game.Players.Localplayer
local playergui = client.PlayerGui


event.OnClientEvent:Connect(function(time)
	playergui.ScreenGui.Frame.TextLabel.Text = ("Time left: " .. time)
end)

This should keep all clients in sync with each other by firing all the clients at the same time