Trying to set PC clock programmatically just before Daylight Saving Time ends <p>To reproduce :</p> <p>1) Add Microsoft.VisualBasic assembly to your project reference</p> <p>2) Change PC timezone to : (GMT+10:00) Canberra, Melbourne, Sydney . Ensure PC is set to automatically adjust clock for daylight savings time. (For this timezone, daylight savings time ends at 3am on 4 Apr 2010.)</p> <p>3) add following code : </p> <pre><code> public void SetNewDateTime(DateTime dt) { Microsoft.VisualBasic.DateAndTime.Today = dt; // ignores time component Microsoft.VisualBasic.DateAndTime.TimeOfDay = dt; // ignores date component } private void button1_Click(object sender, EventArgs e) { DateTime dt = new DateTime(2010, 4, 5, 5, 0, 0); // XX SetNewDateTime(dt); // XX System.Threading.Thread.Sleep(500); DateTime dt2 = new DateTime(2010, 4, 4, 1, 0, 0); SetNewDateTime(dt2); } </code></pre> <p>4) When button 1 is clicked, the PC clock eventually shows 2am, whereas 1 am was expected. (If code marked at "XX" is removed, the clock sometimes shows the correct time of 1 am).</p> <p>Any idea what is happening ? (Or is there a more reliable way of setting the PC clock from C# code ?)</p> <p>TIA.</p> <p><strong>EDIT</strong> :</p> <p>In response to David M, I tried some modified code :</p> <pre><code> private void button1_Click(object sender, EventArgs e) { DateTime dt = new DateTime(2010, 4, 5, 5,0,0, DateTimeKind.Unspecified); SetNewDateTime(dt); System.Threading.Thread.Sleep(500); // type : 2010-04-04T01:00:00 into textBox1 DateTime dt2 = System.Xml.XmlConvert.ToDateTime(textBox1.Text, System.Xml.XmlDateTimeSerializationMode.Unspecified); SetNewDateTime(dt2); } </code></pre> <p>This gets the DateTime input from a textBox. The result was the same.</p>