Expire a perticular data after 1 or 2 or 3 months after submitting into database

using System;
using System.Configuration;
using System.Data;
using System.Data.SqlClient;
using System.IO;
using System.Linq;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.HtmlControls;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Xml.Linq;
using System.Text;
using System.Collections.Generic;

public partial class _123 : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

        //if (Session["XyzUserAuthentication"] == null)
        //{
        //    Response.Redirect("login.aspx");
        //}

    }

protected void RadioButtonList1_SelectedIndexChanged1(object sender, EventArgs e)
{
    if (RadioButtonList1.SelectedValue == "1")
    {
        lblcontact.Visible = true;
        lblcontact.Text = "Seller Info";
        DropDownList1.Enabled = true;
        DropDownList2.Enabled = true;
        txttitle.Enabled = true;
        txtdesc.Enabled = true;
        txtaprox.Enabled = true;
        FuUpload.Enabled = true;
        txtemail.Enabled = true;
        txtfloor.Enabled = true;
        txtno.Enabled = true;
        txtdept.Enabled = true;
        txtcontact.Enabled = true;

    }
    else
    {
        lblcontact.Visible  = true;
        lblcontact.Text = "Contact Info Of Buyer";
        DropDownList1.Enabled = true;
        DropDownList2.Enabled = true;
        txttitle.Enabled = true;
        txtdesc.Enabled = true;
        txtaprox.Enabled = true;
        FuUpload.Enabled = false;
        txtemail.Enabled = true;
        txtfloor.Enabled = true;
        txtno.Enabled = true;
        txtdept.Enabled = true;
        txtcontact.Enabled = true;
    }
}

        protected void btnsave_Click1(object sender, EventArgs e)
        {


            //SqlConnection con = new SqlConnection("Server=traning-pc9;Database=samsung;Integrated Security=True;");
            SqlConnection con = new SqlConnection("Data Source=.\\SQLEXPRESS;AttachDbFilename=D:\\site\\temporary\\App_Data\\Database.mdf;Integrated Security=True;User Instance=True");
            SqlCommand cmd = new SqlCommand();
            con.Open();
            cmd.Connection = con;
            if (RadioButtonList1.SelectedValue == "1")
            {
                if (FuUpload.HasFile)
                {
                    if ((FuUpload.PostedFile.ContentType == "image/jpeg") ||
                    (FuUpload.PostedFile.ContentType == "image/png") ||
                    (FuUpload.PostedFile.ContentType == "image/gif"))
                    {
                        if (Convert.ToInt64(FuUpload.PostedFile.ContentLength) < 1500000)
                        {
                            string date = DateTime.Now.ToString();
                            //string photofolder = Path.Combine(@"D:\site\temporary\Images", User.Identity.Name);
                            string extension = Path.GetExtension(FuUpload.FileName);
                            string uniquefilename = Path.ChangeExtension(FuUpload.FileName, DateTime.Now.Ticks.ToString());
                            //string filename = Path.GetFileName(FuUpload.PostedFile.FileName);
                            FuUpload.SaveAs(Server.MapPath("Images/" + uniquefilename + extension));
                            //FuUpload.SaveAs(Path.Combine(uniquefilename + extension));
                            //FuUpload.SaveAs(Server.MapPath("Images/" + UniqueID +filename));
                            cmd.CommandText = "Insert into post_ad (Category,Sub_Category,Title,Description,Approx_Price,Contact_Name,Email,Phone_Number,Department,Floor,Photos,Buy_Sell_Id,date)values('" + DropDownList1.SelectedValue + "','" + DropDownList2.SelectedValue + "','" + txttitle.Text + "','" + txtdesc.Text + "','" + txtaprox.Text + "','" + txtcontact.Text + "', '" + txtemail.Text + "','" + txtno.Text + "','" + txtdept.Text + "','" + txtfloor.Text + "','"+ "Images/" + uniquefilename + extension + "','" + RadioButtonList1.SelectedValue + "','" + date + "')";
                            cmd.Parameters.AddWithValue("@ImagePath", "Images/" + uniquefilename);
                            int i = cmd.ExecuteNonQuery();
                            if (i > 0)
                            {
                                Label2.Visible = true;
                                Label2.Text = "Data Saved Successfully";
                                btnsave.Text = "Saved";
                            }
                            else
                            {
                                Label2.Visible = true;
                                Label2.Text = "Data not Saved";
                            }
                        }
                            else
                            {
                            Label2.Visible = true;
                            Label2.Text = "file must be less than 5 mb";


                         }


                        }

                    }
                }
}
}
}