How to store datetime into sql database?

I get this exception when I try to save a date into sql database

Arithmetic overflow error converting expression to data type datetime.

The statement has been terminated.

SQL statement :

SqlCommand cmd = new SqlCommand("insert into tbl_purshaseOrders (po_currency,po_paymentTerms,po_deliverydate,po_projectId,po_supplierId,po_notes,po_expiryDate) values (@po_curr开发者_如何学JAVAency,@po_paymentTerms,@po_deliverydate,@po_deliverydate,@po_projectId,@po_notes,@po_expiryDate)", conn);
cmd.CommandType = CommandType.Text;

MessageBox.Show("" + dp_deliveryDate.Text);
cmd.Parameters.AddWithValue("@po_currency", CB_currency.Text);
cmd.Parameters.AddWithValue("@po_paymentTerms", T_paymentTerms.Text.Trim());
cmd.Parameters.AddWithValue("@po_deliverydate", dp_deliveryDate.Text);
cmd.Parameters.AddWithValue("@po_expiryDate", dp_expiryDate.Text);
cmd.Parameters.AddWithValue("@po_projectId", Int32.Parse(T_project.Text.Trim()));
cmd.Parameters.AddWithValue("@po_supplierId", Int32.Parse(T_supplier.Text.Trim()));
cmd.Parameters.AddWithValue("@po_notes", T_notes.Text.Trim());

int val = cmd.ExecuteNonQuery();
if (val > 0)
{
   MessageBox.Show("Added Successfully ", "Done", MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1, MessageBoxOptions.RightAlign | MessageBoxOptions.RtlReading);
   // resetFields();
   GetDate();
} 

• dp_deliveryDate and dp_expiryDate are datepicker fields and have a custom dateformat dd/MM/yyyy**
• po_deliveryDate and po_expiryDate columns are of datetime data type

You should extract the selected Date from the date pickers, not the text

Specify the parameter type:

cmd.Parameters.Add("@ParameterName", SqlDbType.DateTime).Value = "9/15/2011 11:30 AM";

After modifying your code check this :-

enter code hereSqlCommand cmd = new SqlCommand("insert into tbl_purshaseOrders (po_currency,po_paymentTerms,po_deliverydate,po_projectId,po_supplierId,po_notes,po_expiryDate) values (@po_currency,@po_paymentTerms,@po_deliverydate,@po_deliverydate,@po_projectId,@po_notes,@po_expiryDate)", conn);
            cmd.CommandType = CommandType.Text;

            MessageBox.Show("" + dp_deliveryDate.Text);
            cmd.Parameters.AddWithValue("@po_currency", CB_currency.Text);
            cmd.Parameters.AddWithValue("@po_paymentTerms",T_paymentTerms.Text.Trim());
            cmd.Parameters.AddWithValue("@po_deliverydate",Convert.ToDateTime(dp_deliveryDate.Text).toLongDateString());
            cmd.Parameters.AddWithValue("@po_expiryDate", dp_expiryDate.Text);
            cmd.Parameters.AddWithValue("@po_projectId", Int32.Parse(T_project.Text.Trim()));
            cmd.Parameters.AddWithValue("@po_supplierId", Int32.Parse(T_supplier.Text.Trim()));
            cmd.Parameters.AddWithValue("@po_notes", T_notes.Text.Trim());

            int val = cmd.ExecuteNonQuery();
            if (val > 0)
            {
                MessageBox.Show("Added Successfully ", "Done", MessageBoxButtons.OK, MessageBoxIcon.Information, MessageBoxDefaultButton.Button1, MessageBoxOptions.RightAlign | MessageBoxOptions.RtlReading);
               // resetFields();
                GetDate();
            } 

Or

It would be problem of date format also check sending value format same as mentioned in column.

The database doesn't expect that date format. Parse the string in the .NET code:

DateTime deliveryDate = DateTime.ParseExact(dp_deliveryDate.Text, "dd'/'MM'/'yyyy", CultureInfo.InvariantCulture);

Then use the DateTime value in the parameter:

cmd.Parameters.AddWithValue("@po_deliverydate", deliveryDate);

If you are only ever looking at the DateTime in C#, you could store the DateTime as Ticks (see DateTime.Ticks). It's probably better to store the DateTime as a SQL DateTime object, however, so you can read and perform sophisticated queries against it in your database.