Use exactly Local time

Questions
1 
    local time = os.time()
    while time >= 3600 do
        library.pack.time.hours = library.pack.time.hours + 1
        time = time - 3600
    end
    while library.pack.time.hours >= 24 do
        library.pack.time.hours = library.pack.time.hours - 24
    end
    while time >= 60 do
        library.pack.time.minutes = library.pack.time.minutes + 1
        time = time - 60
    end

This returns me 18:16 when using library.pack.time.hours .. library.pack.time.minutes. My local time is 20:16. I mean, local time can be changed!