I need solution for system.formatexception: 'the string was not recognized as a valid datetime. There is an unknown word starting at index 0.'

-------|>f_Patient.dateTimeNOW.Text = this.DGV.CurrentRow.Cells[7].Value.ToString();<|------
  System.FormatException: 'The string was not recognized as a valid DateTime. There is an unknown word starting at index 0.'

private void btn_Update_FromGrid_Click(object sender, EventArgs e)
        {
            Forms.F_Patient f_Patient = new F_Patient();
            f_Patient.btn_Add_NewPatient.Visible = false;
            f_Patient.btn_Delete.Visible = false;
            f_Patient.btn_Search.Visible = false;
            label1.Text = "Update Patient";
            f_Patient.PatientIDTextBox.Text = this.DGV.CurrentRow.Cells[0].Value.ToString();
            f_Patient.PatientTCTextBox.Text = this.DGV.CurrentRow.Cells[1].Value.ToString();
            f_Patient.PatientNameTextBox.Text = this.DGV.CurrentRow.Cells[2].Value.ToString();
            f_Patient.PatientAgeTextBox.Text = this.DGV.CurrentRow.Cells[3].Value.ToString();
            if (this.DGV.CurrentRow.Cells[4].Value.ToString() == "Male")
            {
                f_Patient.radioButton_Male.Checked = true;
            }
            else
            {

                f_Patient.radioButton_Female.Checked = true;

            }
            f_Patient.PatientPhoneTextBox.Text = this.DGV.CurrentRow.Cells[5].Value.ToString();
            f_Patient.comboBox_ShowState.SelectedItem = (this.DGV.CurrentRow.Cells[6].Value);
            f_Patient.dateTimeNOW.Text = this.DGV.CurrentRow.Cells[7].Value.ToString();
            f_Patient.EmailTextBox.Text = this.DGV.CurrentRow.Cells[8].Value.ToString();
            f_Patient.PatientCostTextBox.Text = this.DGV.CurrentRow.Cells[9].Value.ToString();
            f_Patient.PayedTextBox.Text = this.DGV.CurrentRow.Cells[10].Value.ToString();
            f_Patient.RemindTextBox.Text = this.DGV.CurrentRow.Cells[11].Value.ToString();
            byte[] pa_img = (byte[])ShowImage.Show_Patient_Image(Convert.ToInt32(this.DGV.CurrentRow.Cells[0].Value)).Rows[0][0];
            MemoryStream ms = new MemoryStream(pa_img);
            f_Patient.pictureBox1.Image = Image.FromStream(ms);
            f_Patient.NOTES_TextBox.Text = this.DGV.CurrentRow.Cells[12].Value.ToString();
            f_Patient.ShowDialog();
        }