Changing the text of GUI for all players in a server?

I'm a player on ROBLOX who wishes to make a game and have just started on ROBLOX Lua Scripting. I'm not experienced at all and need help.

So I want to make a script that makes the text of TextLabel "TransferRateDisplay" (Path : game.StarterGui.ScreenGui.BottomRightGUI.TransferRateDisplay) to change for all players (to the same value for every player too) in the server after the TimeOfDay reaches midnight for each day.

I've put this script inside the StarterPlayerScripts :

function changeCurrency(a, b, c)
        print("Changing Transfer Rate")
        print(a)
        print(b)
        print(c)
        local TR = game.Workspace.TransferRate.Value
        local TRGui = game.Workspace.Players.LocalPlayer.PlayerGui.ScreenGui.BottomRightGUI.TransferRateDisplay
        local PlusMinus
        local Multiplier
        if (b < 5) then
            Multiplier = 3
        end
        if (b >= 5 or b < 25) then
            Multiplier = 2
        end
        if (b >= 25) then
            Multiplier = 1
        end

        if (c == 1) then
            PlusMinus = 1
        end
        if (c == 2) then
            PlusMinus = -1
        end
        if (a < 70) then
            TR = TR + (Multiplier * PlusMinus)
            if (TR < 8) then
                TR = 8
            end
            if (TR > 25) then
                TR = 25
            end
            TRGui.Text = "Transfer Rate : " .. TR .. "Tx / R$"
        else
            --Nothing Happens!
        end
end
while true do
    game.Lighting:SetMinutesAfterMidnight(game.Lighting:GetMinutesAfterMidnight() + 2.4)
    wait(0.1)
    if (game.Lighting:GetMinutesAfterMidnight() < 1 or game.Lighting:GetMinutesAfterMidnight() > 1439) then
        math.randomseed(tick())
        local a = math.random(1,100)
        local b = math.random(1,100)
        local c = math.random(1,2)
        changeCurrency(a, b, c)
    end
end

So I started a local server of one player in my ROBLOX Studio.

The output in my server view was :

13:34:54.928 - Started network server on XXXXXXXX
13:34:54.929 - Started network server on XXXXXXXX
Loaded gloo library. Type _G.gloo.Help() for help.
Loaded CmdUtl plugin (v5.0.0)
13:34:55.258 - Successfully opened file - C:/Users/User/AppData/Local/Roblox/server.rbxl
13:35:01.463 - New connection from XXXXXXXX

13:35:01.531 - Replication: Can't create default object of type Players
Player -1 added

The output in my player view was :

Loaded gloo library. Type _G.gloo.Help() for help.
Loaded CmdUtl plugin (v5.0.0)
13:35:01.460 - ! Joining game '' place 0 at localhost
13:35:01.461 - Connecting to localhost:XXXXXXXX
13:35:02.300 - Connection accepted from XXXXXXXX

Changing Transfer Rate
19
2
1
13:36:09.846 - Players is not a valid member of Workspace
13:36:09.847 - Script 'Players.Player1.PlayerScripts.LocalScript', Line 7 - global changeCurrency
13:36:09.847 - Script 'Players.Player1.PlayerScripts.LocalScript', Line 47
13:36:09.847 - Stack End