If you want to find back date from current date then you should take DateTime Structure with add days method. Through this method we can add some days in existing date. But if we pass minus sign(-) with integer value in add days method then you get back date. lets take a simple example.
<!DOCTYPE html>
<script runat="server">
protected void Button1_Click(object sender, EventArgs e)
{
DateTime currentdate = DateTime.Now;
Label1.Text = currentdate.ToString()+"<br/>";
Label1.Text += "before 3 days " + currentdate.AddDays(-3);
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Get back Date</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
<br />
<br />
<asp:Button ID="Button1" runat="server" Text="Get Back Date" OnClick="Button1_Click" />
</div>
</form>
</body>
</html>
Complete Code
<%@ Page Language="C#" %><!DOCTYPE html>
<script runat="server">
protected void Button1_Click(object sender, EventArgs e)
{
DateTime currentdate = DateTime.Now;
Label1.Text = currentdate.ToString()+"<br/>";
Label1.Text += "before 3 days " + currentdate.AddDays(-3);
}
</script>
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title>Get back Date</title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Label ID="Label1" runat="server" Text=""></asp:Label>
<br />
<br />
<asp:Button ID="Button1" runat="server" Text="Get Back Date" OnClick="Button1_Click" />
</div>
</form>
</body>
</html>
Code Generate the following output
