Why does the os time only use local time?

local DataStore = game:GetService("DataStoreService"):GetDataStore("LastLogin")


game.Players.PlayerAdded:connect(function(Player)
    wait()
    local LastLogin = DataStore:GetAsync(Player.userId)
    if LastLogin then
        local Seconds = os.time()-LastLogin
        local Minutes = Seconds/60
        local Hours = Minutes/60
        print("It has been: "..Hours.." hours Since your last reward")
        if Hours >= 24 then
            print("You get a daily login award")
            DataStore:SetAsync(Player.userId,os.time())
        end
    else
        DataStore:SetAsync(Player.userId,os.time())
    end
end)

I put this code on a server script in the workspace, but this only works with local time. I know this because i changed my date 1 day forward and it printed that i got an award and last reward was 24h ago.

I want to use server time for this, i think it's based off PST but whatever, as long as its not possible to loophole.