Change system date programmatically

How can I change the local system's date & time programmatically with C#?

Here is where I found the answer.; I have reposted it here to improve clarity.

Define this structure:

[StructLayout(LayoutKind.Sequential)]
public struct SYSTEMTIME
{
	public short wYear;
	public short wMonth;
	public short wDayOfWeek;
	public short wDay;
	public short wHour;
	public short wMinute;
	public short wSecond;
	public short wMilliseconds;
}

Add the following extern method to your class:

[DllImport("kernel32.dll", SetLastError = true)]
public static extern bool SetSystemTime(ref SYSTEMTIME st);

Then call the method with an instance of your struct like this:

SYSTEMTIME st = new SYSTEMTIME();
st.wYear = 2009; // must be short
st.wMonth = 1;
st.wDay = 1;
st.wHour = 0;
st.wMinute = 0;
st.wSecond = 0;

SetSystemTime(ref st); // invoke this method.

A lot of great viewpoints and approaches are already here, but here are some specifications that are currently left out and that I feel might trip up and confuse some people.

1. On Windows Vista, 7, 8 OS this will require a UAC Prompt in order to obtain the necessary administrative rights to successfully execute the SetSystemTime function. The reason is that calling process needs the SE_SYSTEMTIME_NAME privilege.
2. The SetSystemTime function is expecting a SYSTEMTIME struct in coordinated universal time (UTC). It will not work as desired otherwise.

Depending on where/ how you are getting your DateTime values, it might be best to play it safe and use ToUniversalTime() before setting the corresponding values in the SYSTEMTIME struct.

Code example:

DateTime tempDateTime = GetDateTimeFromSomeService();
DateTime dateTime = tempDateTime.ToUniversalTime();

SYSTEMTIME st = new SYSTEMTIME();
// All of these must be short
st.wYear = (short)dateTime.Year;
st.wMonth = (short)dateTime.Month;
st.wDay = (short)dateTime.Day;
st.wHour = (short)dateTime.Hour;
st.wMinute = (short)dateTime.Minute;
st.wSecond = (short)dateTime.Second;

// invoke the SetSystemTime method now
SetSystemTime(ref st); 

You can use a call to a DOS command but the invoke of the function in the windows dll is a better way to do it.

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;
};

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

[DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)]
public extern static bool Win32SetSystemTime(ref SystemTime sysTime);

private void button1_Click(object sender, EventArgs e)
{
    // Set system date and time
    SystemTime updatedTime = new SystemTime();
    updatedTime.Year = (ushort)2009;
    updatedTime.Month = (ushort)3;
    updatedTime.Day = (ushort)16;
    updatedTime.Hour = (ushort)10;
    updatedTime.Minute = (ushort)0;
    updatedTime.Second = (ushort)0;
    // Call the unmanaged function that sets the new date and time instantly
    Win32SetSystemTime(ref updatedTime);
}  

Use this function to change the time of system (tested in window 8)

 void setDate(string dateInYourSystemFormat)
    {
        var proc = new System.Diagnostics.ProcessStartInfo();
        proc.UseShellExecute = true;
        proc.WorkingDirectory = @"C:\Windows\System32";
        proc.CreateNoWindow = true;
        proc.FileName = @"C:\Windows\System32\cmd.exe";
        proc.Verb = "runas";
        proc.Arguments = "/C date " + dateInYourSystemFormat;
        try
        {
            System.Diagnostics.Process.Start(proc);
        }
        catch
        {
            MessageBox.Show("Error to change time of your system");
            Application.ExitThread();
        }
    }
void setTime(string timeInYourSystemFormat)
    {
        var proc = new System.Diagnostics.ProcessStartInfo();
        proc.UseShellExecute = true;
        proc.WorkingDirectory = @"C:\Windows\System32";
        proc.CreateNoWindow = true;
        proc.FileName = @"C:\Windows\System32\cmd.exe";
        proc.Verb = "runas";
        proc.Arguments = "/C time " + timeInYourSystemFormat;
        try
        {
            System.Diagnostics.Process.Start(proc);
        }
        catch
        {
            MessageBox.Show("Error to change time of your system");
            Application.ExitThread();
        }
    }

Example: Call in load method of form setDate("5-6-92"); setTime("2:4:5 AM");

1. PInvoke to call Win32 API SetSystemTime,(example)
2. System.Management classes with WMI class Win32_OperatingSystem and call SetDateTime on that class.

Both require that the caller has been granted SeSystemTimePrivilege and that this privilege is enabled.

Since I mentioned it in a comment, here's a C++/CLI wrapper:

#include <windows.h>
namespace JDanielSmith
{
	public ref class Utilities abstract sealed /* abstract sealed = static */
	{
	public:
		CA_SUPPRESS_MESSAGE("Microsoft.Security", "CA2122:DoNotIndirectlyExposeMethodsWithLinkDemands")
		static void SetSystemTime(System::DateTime dateTime) {
			LARGE_INTEGER largeInteger;
			largeInteger.QuadPart = dateTime.ToFileTimeUtc(); // "If your compiler has built-in support for 64-bit integers, use the QuadPart member to store the 64-bit integer."

    
			FILETIME fileTime; // "...copy the LowPart and HighPart members [of LARGE_INTEGER] into the FILETIME structure."
			fileTime.dwHighDateTime = largeInteger.HighPart;
			fileTime.dwLowDateTime = largeInteger.LowPart;


			SYSTEMTIME systemTime;
			if (FileTimeToSystemTime(&fileTime, &systemTime))
			{
				if (::SetSystemTime(&systemTime))
					return;
			}


			HRESULT hr = HRESULT_FROM_WIN32(GetLastError());
			throw System::Runtime::InteropServices::Marshal::GetExceptionForHR(hr);
		}
	};
}

The C# client code is now very simple:

JDanielSmith.Utilities.SetSystemTime(DateTime.Now);

A copy/paste class for anyone else who's looking for one

using System;
using System.ComponentModel;
using System.Runtime.InteropServices;

public static class SystemDateTime
{
    [DllImport("kernel32.dll", EntryPoint = "SetSystemTime", SetLastError = true)]
    private static extern bool Win32SetSystemTime(ref SystemTime sysTime);

    [StructLayout(LayoutKind.Sequential)]
    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;
    };

    public static void SetSystemDateTime(int year, int month, int day, int hour,
        int minute, int second, int millisecond)
    {
        SystemTime updatedTime = new SystemTime
        {
            Year = (ushort) year,
            Month = (ushort) month,
            Day = (ushort) day,
            Hour = (ushort) hour,
            Minute = (ushort) minute,
            Second = (ushort) second,
            Millisecond = (ushort) millisecond
        };

        // If this returns false, then the problem is most likely that you don't have the 
        // admin privileges required to set the system clock
        if (!Win32SetSystemTime(ref updatedTime))
        {
            throw new Win32Exception(Marshal.GetLastWin32Error());
        }
    }

    public static void SetSystemDateTime(DateTime dateTime)
    {
        SetSystemDateTime(dateTime.Year, dateTime.Month, dateTime.Day, dateTime.Hour, dateTime.Minute,
            dateTime.Second, dateTime.Millisecond);
    }
}

Be Careful!. If you delete unused property from the structure, it sets the time wrong. I ve lost 1 day because of this. I think order of the structure is important.

This is correct structure:

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;
            
        };

If you run the SetSystemTime(), it works as expected. For test I set the time as below;

SystemTime st = new SystemTime();
st.Year = 2019;
st.Month = 10;
st.Day = 15;
st.Hour = 10;
st.Minute = 20;
st.Second = 30;
    
SetSystemTime(ref st);

The time set: 15.10.2019 10:20, its ok.

But I delete DayOfWeek property which not used ;

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

SystemTime st = new SystemTime();
    st.Year = 2019;
    st.Month = 10;
    st.Day = 15;
    st.Hour = 10;
    st.Minute = 20;
    st.Second = 30;
        
    SetSystemTime(ref st);

Run same code but the time set to: 10.10.2019 20:30

Please be careful order and all fields of SystemTime structure. Yusuf

> proc.Arguments = "/C Date:" + dateInYourSystemFormat;

This Is Work Function:

void setDate(string dateInYourSystemFormat)
{
    var proc = new System.Diagnostics.ProcessStartInfo();
    proc.UseShellExecute = true;
    proc.WorkingDirectory = @"C:\Windows\System32";
    proc.CreateNoWindow = true;
    proc.FileName = @"C:\Windows\System32\cmd.exe";
    proc.Verb = "runas";
    proc.Arguments = "/C Date:" + dateInYourSystemFormat;
    try
    {
        System.Diagnostics.Process.Start(proc);
    }
    catch
    {
        MessageBox.Show("Error to change time of your system");
        Application.ExitThread();
    }
}