مشكلة في التاريخ

using System;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Windows;
using System.Windows.Controls;
using System.Windows.Documents;
using System.Windows.Input;
using System.Windows.Media;
using System.Windows.Media.Animation;
using System.Windows.Shapes;
using Microsoft.Phone.Controls;
using Microsoft.Phone.Scheduler;
using System.IO.IsolatedStorage;
using System.IO;

namespace ReminderSample
{
public partial class AddReminder : PhoneApplicationPage
{
public AddReminder()
{
InitializeComponent();
}

/// <summary>
/// for isolated file
/// </summary>
// IsolatedStorageFile myIsolatedStorage = IsolatedStorageFile.GetUserStoreForApplication();
private IsolatedStorageSettings appSettingsA = IsolatedStorageSettings.ApplicationSettings;

private void ApplicationBarSaveButton_Click(object sender, EventArgs e)
{
// Generate a unique name for the new reminder. You can choose a
// name that is meaningful for your app, or just use a GUID.
String name = System.Guid.NewGuid().ToString();
String name2 = System.Guid.NewGuid().ToString();

// Get the begin time for the reminder by combining the DatePicker
// value and the TimePicker value.
DateTime time = (DateTime)beginTimePicker.Value;
DateTime date = (DateTime)beginDatePicker.Value;//birthdate
DateTime date2 = date.AddMonths(2);
DateTime beginTime = date + time.TimeOfDay;
DateTime V2Time = date2 + time.TimeOfDay;//المشكلة من date2


/////date2 convert to string thane add to isolated file////

string vChvDate2 = date2.ToString("dd/MM/yyyy");
string BirthDate = date.ToString("dd/MM/yyyy");

try
{

appSettingsA.Add("birth", BirthDate);
appSettingsA.Add("V2", vChvDate2);

}
catch
//catch(ArgumentException ex)
{
//string c = "error";
//MessageBox.Show(c);

}


// Make sure that the begin time has not already passed.
if (beginTime < DateTime.Now)
{
MessageBox.Show("the begin date must be in the future.");
return;
}

// Get the expiration time for the reminder
DateTime dateX = (DateTime)expirationDatePicker.Value;
DateTime timeX = (DateTime)expirationTimePicker.Value;
DateTime expirationTime = dateX + timeX.TimeOfDay;

// Make sure that the expiration time is after the begin time.
if (expirationTime < beginTime)
{
MessageBox.Show("expiration time must be after the begin time.");
return;
}

// Determine which recurrence radio button is checked.
RecurrenceInterval recurrence = RecurrenceInterval.None;
if (dailyRadioButton.IsChecked == true)
{
recurrence = RecurrenceInterval.Daily;
}
else if (weeklyRadioButton.IsChecked == true)
{
recurrence = RecurrenceInterval.Weekly;
}
else if (monthlyRadioButton.IsChecked == true)
{
recurrence = RecurrenceInterval.Monthly;
}
else if (endOfMonthRadioButton.IsChecked == true)
{
recurrence = RecurrenceInterval.EndOfMonth;
}
else if (yearlyRadioButton.IsChecked == true)
{
recurrence = RecurrenceInterval.Yearly;
}


// Create a Uri for the page that will be launched if the user
// taps on the reminder. Use query string parameters to pass
// content to the page that is launched.
//string param1Value = param1TextBox.Text;
//string param2Value = param2TextBox.Text;
//string queryString = "";
//if (param1Value != "" && param2Value != "")
//{
// queryString = "?param1=" + param1Value + "&param2=" + param2Value;
//}
//else if(param1Value != "" || param2Value != "")
//{
// queryString = (param1Value!=null) ? "?param1="+param1Value : "?param2="+param2Value;
//}

//Uri navigationUri = new Uri("/ShowParams.xaml" + queryString, UriKind.Relative);

Reminder reminder = new Reminder(name);
reminder.Title = titleTextBox.Text;
reminder.Content = contentTextBox.Text;
reminder.BeginTime = beginTime;
reminder.ExpirationTime = expirationTime;
reminder.RecurrenceType = recurrence;
// reminder.NavigationUri = navigationUri;


// date2 V2Time
Reminder reminder2 = new Reminder(name2);
reminder2.Title = titleTextBox.Text;
reminder2.Content = contentTextBox.Text;
reminder2.BeginTime = V2Time;//هنا المشكلة
reminder2.ExpirationTime = expirationTime;
reminder2.RecurrenceType = recurrence;
// reminder2.NavigationUri = navigationUri;

// Register the reminder with the system.
ScheduledActionService.Add(reminder);
ScheduledActionService.Add(reminder2);

// Navigate back to the main reminder list page.
NavigationService.GoBack();

}
}
}