Windows Forms: How to change system date in C#

Dragging DateTimePicker, Button from the Visual Studio toolbox into your form designer, then design a simple UI allows you to change the system date as shown below.

Defining a struct datetime as shown below.

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

How to change system date and time using c#

Next, We will use Win32 API to set the system date time.

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

Adding a click event handler to the Save button allows you to change the system date.

//c# set system time windows 10
private void btnSave_Click(object sender, EventArgs e)
{
    SystemDate systemDate = new SystemDate();
    systemDate.Month = (ushort)dateTimePicker.Value.Month;
    systemDate.Day = (ushort)dateTimePicker.Value.Day;
    systemDate.Year = (ushort)dateTimePicker.Value.Year;
    var result = SetSystemTime(ref systemDate);
    if (result)
        MessageBox.Show("You have successfully changed the system date.", "Message", MessageBoxButtons.OK, MessageBoxIcon.Information);
}

If you want to change system date time in c#, you can modify your code as shown below.

DateTime date = new DateTime(2020, 13, 9, 11, 30, 15, 0, DateTimeKind.Utc);
SystemDate systime = new SystemDate(date);
SetSystemTime(ref systime);

and don't forget to add a constructor to your SystemDate struct.

public SystemDate(DateTime dt)
{
    Year = (ushort)dt.Year;
    Month = (ushort)dt.Month;
    DayOfWeek = (ushort)dt.DayOfWeek;
    Day = (ushort)dt.Day;
    Hour = (ushort)dt.Hour;
    Minute = (ushort)dt.Minute;
    Second = (ushort)dt.Second;
    Milliseconds = (ushort)dt.Millisecond;
}

Through this post you can easily set system date time in windows using c#.