bind date and day name to a single comobo box based on month

Try something like this:

    public partial class Form1 : Form

    {

        public Form1()

        {

            InitializeComponent();

        }

        private void Form1_Load(object sender, EventArgs e)

        {

            int[] years = { 2011, 2012, 2013, 2014 }; // or whatever

            comboBox1.DataSource = years;

            string[] months = { "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December" };

            comboBox2.DataSource = months;

            comboBox1.SelectedIndex = 3; // say

            comboBox2.SelectedIndex = 0;

        }

        private void comboBox1_SelectedIndexChanged(object sender, EventArgs e)

        {

            GetDays();

        }

        private void comboBox2_SelectedIndexChanged(object sender, EventArgs e)

        {

            GetDays();

        }

        private void GetDays()

        {

            int year = 0;

            int month = 0;

            if (comboBox1.SelectedIndex > -1 && comboBox2.SelectedIndex > -1)

            {

                year = int.Parse(comboBox1.SelectedItem.ToString());

                month = comboBox2.SelectedIndex + 1;               

            }

            else

            {

                return;

            }

            int daysInMonth = DateTime.DaysInMonth(year, month);

            string[] days = new string[daysInMonth];

            DateTime dt = new DateTime(year, month, 1);

            for (int i = 0; i < daysInMonth; i++)

            {

                days[i] = String.Format("{0, -2} {1}", i + 1, dt.DayOfWeek);

                dt = dt.AddDays(1);

            }

            comboBox3.DataSource = days;

            comboBox3.SelectedIndex = 0;

        }

    }