This program will change the time and date on a PC. 

Code:

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace TimeAndDateChanger
{
    public partial class frmTimeandDate : Form
    {
        public frmTimeandDate()
        {
            InitializeComponent();
        }
 
      
        Decimal  Hour, Minutes;
        decimal  GetYear,getmonth,getdate;
        Int32 month;

     
        private void buttonsettime_Click(object sender, EventArgs e)
        {
            StreamWriter streamtext;
            //write time in the bat file
            File.WriteAllText("man.bat", "time");
            Process myprocess = new Process();
            myprocess.StartInfo.CreateNoWindow = true;
            myprocess.StartInfo.RedirectStandardInput = true;
            myprocess.StartInfo.RedirectStandardOutput = true;
            myprocess.StartInfo.UseShellExecute = false;
            myprocess.StartInfo.FileName = "man.bat";
            //start the bat file
            myprocess.Start();
            streamtext = myprocess.StandardInput;
            //write the numeric values into the streamwriter
           streamtext.Write(numericUpDownhour.Value  + ":" + numericUpDownminutes.Value );
            streamtext.Flush();
            streamtext.Close();
        }

        private void buttonRestoretime_Click(object sender, EventArgs e)
        {
            StreamWriter streamtext;
            File.WriteAllText("man.bat", "time");
            //create a new process
            Process myprocess = new Process();
            //create nowindow of the batch file
            myprocess.StartInfo.CreateNoWindow = true;
            myprocess.StartInfo.RedirectStandardInput = true;
            myprocess.StartInfo.RedirectStandardOutput = true;
            myprocess.StartInfo.UseShellExecute = false;
            myprocess.StartInfo.FileName = "man.bat";
            myprocess.Start();
            streamtext = myprocess.StandardInput;

            streamtext.Write(Hour + ":" + Minutes );
            //save the changes made
            streamtext.Flush();
            streamtext.Close();
        }

        private void buttonExit_Click(object sender, EventArgs e)
        {
            //delete the bat file
            File.Delete("man.bat");
            this.Close();

        }
        private void frmTimeandDate_Load(object sender, EventArgs e)
        {
            getmonth = comboBoxmonths.SelectedIndex = DateTime.Now.Month - 1;
            Hour = numericUpDownhour.Value = DateTime.Now.Hour;
            getdate = numericUpDowndate.Value = Convert.ToInt32(DateTime.Now.Date.ToString().Substring(0, 2).Trim());
            Minutes = numericUpDownminutes.Value = DateTime.Now.Minute;
            GetYear = numericUpDownyear.Value = DateTime.Now.Year;
            tmTimer.Enabled = true;
        }

        private void btnSetDate_Click(object sender, EventArgs e)
        {
            StreamWriter streamtext;
            File.WriteAllText("man.bat", "date");
            //create a new process
            Process myprocess = new Process();
            //create nowindow of the batch file
            myprocess.StartInfo.CreateNoWindow = true;
            myprocess.StartInfo.RedirectStandardInput = true;
            myprocess.StartInfo.RedirectStandardOutput = true;
            myprocess.StartInfo.UseShellExecute = false;
            myprocess.StartInfo.FileName = "man.bat";
            myprocess.Start();
            streamtext = myprocess.StandardInput;

            streamtext.Write(numericUpDowndate.Value + "-" + month + "-" + numericUpDownyear.Value);
            //save the changes made
            streamtext.Flush();
            streamtext.Close();
        }

        private void tmTimer_Tick(object sender, EventArgs e)
        {
            //display the current time
            labelcurrenttime.Text = "The current time is " + DateTime.Now.ToShortTimeString();
            //display the current date
            labelcurrentdate.Text = "The current date is " + DateTime.Now.ToShortDateString();
        }

        private void comboBoxmonths_SelectedIndexChanged(object sender, EventArgs e)
        {
            try
            {
                month = comboBoxmonths.SelectedIndex + 1;
                numericUpDowndate.Maximum = Application.CurrentCulture.Calendar.GetDaysInMonth((Int32)numericUpDownyear.Value, comboBoxmonths.SelectedIndex + 1);
            }catch (ArgumentOutOfRangeException)
            {
                numericUpDowndate.Maximum = Application.CurrentCulture.Calendar.GetDaysInMonth(DateTime .Now .Year , comboBoxmonths.SelectedIndex + 1);
            
            }
        }

       
        Int32 dmonth;
        private void buttonRestoredate_Click(object sender, EventArgs e)
        {
            StreamWriter streamtext;
            File.WriteAllText("man.bat", "date");
            //create a new process
            Process myprocess = new Process();
            //create nowindow of the batch file
            myprocess.StartInfo.CreateNoWindow = true;
            myprocess.StartInfo.RedirectStandardInput = true;
            myprocess.StartInfo.RedirectStandardOutput = true;
            myprocess.StartInfo.UseShellExecute = false;
            myprocess.StartInfo.FileName = "man.bat";
            myprocess.Start();
            streamtext = myprocess.StandardInput;
            dmonth =Convert .ToInt32 ( getmonth + 1);
            //set the time 
            streamtext.Write(getdate  + "-" + dmonth   + "-" + GetYear );
            //save the changes made
            streamtext.Flush();
            streamtext.Close();
            numericUpDownyear.Value  = GetYear;
            numericUpDowndate.Value  = getdate;
            comboBoxmonths.SelectedIndex =(Int32 ) getmonth;
        }
     
    }
}