Winform how to add time stamp to data grid when edited

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

namespace GridTimeStamp
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        private void Form1_Load(object sender, EventArgs e)
        {
            for (int i = 1; i < 5; i++)
            {
                dataGridView1.Rows.Add(i.ToString(), "Data" + i.ToString(),DateTime.Now.ToFileTimeUtc());
            }
        }

        private void dataGridView1_CellEndEdit(object sender, DataGridViewCellEventArgs e)
        {
            if (e.ColumnIndex != 2)
                dataGridView1.Rows[e.RowIndex].Cells[2].Value = DateTime.Now.ToFileTimeUtc();
        }
    }
}