Getting current GMT time

Question

Is there a method in C# that returns the UTC (GMT) time zone? Not based on the system's time.

Basically I want to get the correct UTC time even if my system time is not right.

Just a quick note: UTC time and GMT time are not always the same thing. UTC is easy in .net, GMT less so. — Yes - that Jake., Feb 05 '09 at 17:01
Why can't you rely on the system having the right time synchronized over NTP? — Tadeusz A. Kadłubowski, Jun 11 '12 at 17:59

score 54 · Answer 1 · answered Mar 12 '12 at 15:30

54

Instead of calling

DateTime.Now.ToUniversalTime()

you can call

DateTime.UtcNow

Same thing but shorter :) Documentation here.

answered Mar 12 '12 at 15:30

Alex

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1

This is based on system time looking at the docs? `Gets a DateTime object that is set to the current date and time on this computer, expressed as the Coordinated Universal Time (UTC)`. The question was how to get time in UTC without relying on the system clock. Obviously I'm confused. – TEK Mar 16 '16 at 10:49

score 20 · Answer 2 · answered Feb 05 '09 at 16:59

Not based on the system's time? You'd need to make a call to a network time service or something similar. You could write an NTP client, or just screenscrape World Clock ;)

I don't believe .NET has an NTP client built in, but there are quite a few available.

score 7 · Answer 3 · edited May 12 '12 at 17:43

I use this from UNITY

//Get a NTP time from NIST
//do not request a nist date more than once every 4 seconds, or the connection will be refused.
//more servers at tf.nist.goc/tf-cgi/servers.cgi
public static DateTime GetDummyDate()
{
    return new DateTime(1000, 1, 1); //to check if we have an online date or not.
}
public static DateTime GetNISTDate()
{
    Random ran = new Random(DateTime.Now.Millisecond);
    DateTime date = GetDummyDate();
    string serverResponse = string.Empty;

    // Represents the list of NIST servers
    string[] servers = new string[] {
        "nist1-ny.ustiming.org",
        "time-a.nist.gov",
        "nist1-chi.ustiming.org",
        "time.nist.gov",
        "ntp-nist.ldsbc.edu",
        "nist1-la.ustiming.org"                         
    };

    // Try each server in random order to avoid blocked requests due to too frequent request
    for (int i = 0; i < 5; i++)
    {
        try
        {
            // Open a StreamReader to a random time server
            StreamReader reader = new StreamReader(new System.Net.Sockets.TcpClient(servers[ran.Next(0, servers.Length)], 13).GetStream());
            serverResponse = reader.ReadToEnd();
            reader.Close();

            // Check to see that the signature is there
            if (serverResponse.Length > 47 && serverResponse.Substring(38, 9).Equals("UTC(NIST)"))
            {
                // Parse the date
                int jd = int.Parse(serverResponse.Substring(1, 5));
                int yr = int.Parse(serverResponse.Substring(7, 2));
                int mo = int.Parse(serverResponse.Substring(10, 2));
                int dy = int.Parse(serverResponse.Substring(13, 2));
                int hr = int.Parse(serverResponse.Substring(16, 2));
                int mm = int.Parse(serverResponse.Substring(19, 2));
                int sc = int.Parse(serverResponse.Substring(22, 2));

                if (jd > 51544)
                    yr += 2000;
                else
                    yr += 1999;

                date = new DateTime(yr, mo, dy, hr, mm, sc);

                // Exit the loop
                break;
            }
        }
        catch (Exception ex)
        {
            /* Do Nothing...try the next server */
        }
    }
return date;
}

You may want to use `pool.ntp.org` to let it choose a server for you — abatishchev, Mar 12 '12 at 15:39
@abatishchev I tried to use your idea. But , it didn't work. I got the error message "No connection could be made because the target machine actively refused it 140.109.1.10:13"" — prabhakaran, May 12 '12 at 12:09

score 3 · Answer 4 · answered Feb 05 '09 at 17:00

3

If I were to wager a guess for how to get a guaranteed accurate time, you'd have to find / write some NNTP class to get the time off of a time server.

If you search C# NTP on google you can find a few implementations, otherwise check the NTP protocol.

answered Feb 05 '09 at 17:00

Sciolist

1,829
14
10

score 3 · Answer 5 · answered Feb 05 '09 at 17:01

3

If your system time is not right, nothing that you get out of the DateTime class will help. Your system can sync the time with time servers though, so if that is turned on, the various DateTime UTC methods/properties will return the correct UTC time.

answered Feb 05 '09 at 17:01

Rob Prouse

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score 0 · Answer 6 · answered Nov 18 '20 at 08:18

You can simply hardcode a base DateTime in and calculate the difference between your given DateTime with that base to determine the precise desired DateTime as below code:

    string format = "ddd dd MMM yyyy HH:mm:ss";     
    string utcBaseStr = "Wed 18 Nov 2020 07:31:34";
    string newyorkBaseStr = "Wed 18 Nov 2020 02:31:34";     
    string nowNewyorkStr = "Wed 18 Nov 2020 03:06:47";
    
    DateTime newyorkBase = DateTime.ParseExact(newyorkBaseStr, format, CultureInfo.InvariantCulture);
    DateTime utcBase = DateTime.ParseExact(utcBaseStr, format, CultureInfo.InvariantCulture);
    DateTime now = DateTime.ParseExact(nowNewyorkStr, format, CultureInfo.InvariantCulture);
    
    var diffMiliseconds = (now - newyorkBase).TotalMilliseconds;
    DateTime nowUtc = utcBase.AddMilliseconds(diffMiliseconds);
    
    Console.WriteLine("Newyork Base = " + newyorkBase);     
    Console.WriteLine("UTC Base = " + utcBase);
    Console.WriteLine("Newyork Now = " + now);      
    Console.WriteLine("Newyork UTC = " + nowUtc);

The output of above code is as follow:

Newyork Base = 11/18/2020 2:31:34 AM
UTC Base = 11/18/2020 7:31:34 AM
Newyork Now = 11/18/2020 3:06:47 AM
Newyork UTC = 11/18/2020 8:06:47 AM

Getting current GMT time

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