How do I get the server time or the current time of day and change in the system via code?

Code in VB.NET Source: link

 Public Shared Function GetNetworkTime() As DateTime
        'Servidor nacional para melhor latência
        Const ntpServer As String = "a.ntp.br"

        ' Tamanho da mensagem NTP - 16 bytes (RFC 2030)
        Dim ntpData = New Byte(47) {}

        'Indicador de Leap (ver RFC), Versão e Modo
        ntpData(0) = &H1B
        'LI = 0 (sem warnings), VN = 3 (IPv4 apenas), Mode = 3 (modo cliente)
        Dim addresses = Dns.GetHostEntry(ntpServer).AddressList

        '123 é a porta padrão do NTP
        Dim ipEndPoint = New IPEndPoint(addresses(0), 123)
        'NTP usa UDP
        Dim socket = New Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp)

        socket.Connect(ipEndPoint)

        'Caso NTP esteja bloqueado, ao menos nao trava o app
        socket.ReceiveTimeout = 3000

        socket.Send(ntpData)
        socket.Receive(ntpData)
        socket.Close()

        'Offset para chegar no campo "Transmit Timestamp" (que é
        'o do momento da saída do servidor, em formato 64-bit timestamp
        Const serverReplyTime As Byte = 40

        'Pegando os segundos
        Dim intPart As ULong = BitConverter.ToUInt32(ntpData, serverReplyTime)

        'e a fração de segundos
        Dim fractPart As ULong = BitConverter.ToUInt32(ntpData, serverReplyTime + 4)

        'Passando de big-endian pra little-endian
        intPart = SwapEndianness(intPart)
        fractPart = SwapEndianness(fractPart)

        Dim milliseconds = (intPart * 1000) + ((fractPart * 1000) / &H100000000L)

        'Tempo em **UTC**
        Dim networkDateTime = (New DateTime(1900, 1, 1, 0, 0, 0, DateTimeKind.Utc)).AddMilliseconds(CLng(milliseconds))

        Return networkDateTime.ToLocalTime()
    End Function

    ' stackoverflow.com/a/3294698/162671
    Private Shared Function SwapEndianness(x As ULong) As UInteger
        Return CUInt(((x And &HFF) << 24) + ((x And &HFF00) << 8) + ((x And &HFF0000) >> 8) + ((x And &HFF000000UI) >> 24))
    End Function

class Program
{
    //necessário privilégio administrador
    [DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)]
    public extern static bool Win32SetSystemTime(ref SystemTime sysTime);

    [DllImport("kernel32.dll", EntryPoint = "GetSystemTime", SetLastError = true)]
    public extern static void Win32GetSystemTime(ref SystemTime sysTime);

    public struct SystemTime
    {
        public ushort Year;
        public ushort Month;
        public ushort DayOfWeek;
        public ushort Day;
        public ushort Hour;
        public ushort Minute;
        public ushort Second;
        public ushort Millisecond;
    }

    private static void Main()
    {
        //servidor intranet "user-PC" (local)
        //a.ntp.br (internet) 
        //var localDateTime = PegarDtHoraRedeLocal("user-PC");
        var horaAtual = PegarDtHoraAtualizada("a.ntp.br");

        //AJUSTA HORA BASEADO NO FUSO HORARIO DO COMPUTADOR LOCAL
        SetTime(horaAtual.ToUniversalTime());
        Console.ReadKey();
    }

    public static DateTime PegarDtHoraAtualizada(string ntpServer)
    {
        var ntpData = new byte[48];
        ntpData[0] = 0x1B; //LeapIndicator = 0 (no warning), VersionNum = 3 (IPv4 only), Mode = 3 (Client Mode)

        //somente IPV4
        var addresses = Dns.GetHostEntry(ntpServer).AddressList.First(a => a.AddressFamily == AddressFamily.InterNetwork);

        var ipEndPoint = new IPEndPoint(addresses, 123);
        var socket = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

        socket.ReceiveTimeout = 5000; //5 segundos timeout
        socket.Connect(ipEndPoint);
        socket.Send(ntpData);
        socket.Receive(ntpData);
        socket.Close();

        ulong intPart = (ulong)ntpData[40] << 24 | (ulong)ntpData[41] << 16 | (ulong)ntpData[42] << 8 | ntpData[43];
        ulong fractPart = (ulong)ntpData[44] << 24 | (ulong)ntpData[45] << 16 | (ulong)ntpData[46] << 8 | ntpData[47];

        var milliseconds = (intPart * 1000) + ((fractPart * 1000) / 0x100000000L);
        var networkDateTime = (new DateTime(1900, 1, 1)).AddMilliseconds((long) milliseconds).ToLocalTime();

        //ajustando para hora brasil teste ajuste independente do fuso horario
        //networkDateTime = DateTime.ParseExact(networkDateTime.ToString(), "dd/M/yyyy HH:mm:ss", CultureInfo.InvariantCulture, DateTimeStyles.AssumeUniversal);
        return networkDateTime;
    }

    private static void SetTime(DateTime dataHoraAtualizada)
    {
        // Prepare native method with the defined structure.
        var st = new SystemTime
        {
            Year = (ushort) (dataHoraAtualizada.Year),
            Month = (ushort) (dataHoraAtualizada.Month),
            Hour = (ushort) (dataHoraAtualizada.Hour),
            Day = (ushort) (dataHoraAtualizada.Day),
            Minute = (ushort) (dataHoraAtualizada.Minute),
            Second = (ushort) (dataHoraAtualizada.Second)
        };

        // Set the system date time.
        var resp = Win32SetSystemTime(ref st);
        Debug.Print(resp.ToString());
    }
}

  

I need to update an O.S system with the time of another micro, if this   another micro would be a server. I would like to do this via code.

var localDateTime = PegarDtHoraRedeLocal("user-PC"); //user-PC: nome servidor sua rede local
//AJUSTA HORA BASEADO NO FUSO HORARIO DO COMPUTADOR LOCAL
SetTime(horaAtual.ToUniversalTime());

OBS:

To configure WIN7 (as NTP server - Network Time Protocol) follow the steps below:

3.1 Stop the service (W32Time - Windows Time), either by service manager or by net stop w32time command prompt

3.2 Open the windows registry regedit.exe

3.3 Navigate to the HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ Services \ W32Time \ Config \ AnnounceFlags key and change the value of 10 to 5 br> 3.4 Navigate to the HKEY_LOCAL_MACHINE \ SYSTEM \ CurrentControlSet \ services \ W32Time \ TimeProviders \ NtpServer key and change the value to 1

3.5 Start the service (W32Time - Windows Time) net start w32time

3.6 To verify that the NTP server is configured correctly, type in the command prompt w32tm / query / configuration and see if the image below appears is configured

  

Anothermethodthatwouldalsohelpwouldbetopicktherighttimeofthedayand  comparetothatoftheComputerthatwillberunningtheprogram.

Hereyougettherighttimeofthedayandcancomparewithyourserver@felipe-walleg

varhoraAtual=PegarDtHoraAtualizada("a.ntp.br"); //Hora atualizada pela internet    
//AJUSTA HORA BASEADO NO FUSO HORARIO DO COMPUTADOR LOCAL
SetTime(horaAtual.ToUniversalTime());

Sources:
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