You can try something like this. This is just a sample code for your thought you can modify this code based on your need.
private void UpdateGrid(DateTime time, int noOfDays)
{
for (int i = 1; i <= noOfDays; i++)
{
DateTime newDate = time.AddDays(i);
for (int newIndex = 0; newIndex < 3; newIndex++)
{
DataGridViewRow row = new DataGridViewRow();
row.Cells[0].Value = newDate.ToShortDateString();
row.Cells[1].Value = newIndex;
this.dataGridView1.Rows.Add(row);
}
}
}