C#

UK
  -london
      -london 1
      -london --
      -london 100
  -Newcastle
      -Newcastle 1
      -Newcastle 2
      -Newcastle 3
  -liverpool
USA
  -New york
  -califonia
China
  -one
  -two

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;

namespace WindowsFormsApplication7
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }

        DateTime[] start = new DateTime[] { new DateTime(2000, 1, 1), new DateTime(2004, 1, 1),  
                                         new DateTime(2004, 1, 1), new DateTime(2008, 1, 1) };
        DateTime[] end   = new DateTime[] { new DateTime(2002, 1, 1), new DateTime(2006, 1, 1),           
                                            new DateTime(2006, 1, 1), new DateTime(2010, 1, 1) };

        int timeDifference = 0;
        TimeSpan timespan;

     
        private void button1_Click(object sender, EventArgs e)
        {
            for (int i=0; i<end.Length-2; i++)
            {
    if (end[i] < end[i + 1] && start[i] <start[i +="" 1]="" &&="" start[i="" 1]<="end[i])
" {
="" timespan="(end[i]" -="" start[i])="" (end[i="" end[i]);
="" }

="" if="" (end[i]="">= end[i + 1] && start[i] <= start[i + 1])          
                {
                    timespan = (end[i] - start[i]);
                }
    if (end[i] > end[i + 1] && start[i] > start[i + 1] && start[i] <= end[i + 1])         
                {
                    timespan = (end[i] - start[i]) + (end[i + 1] - end[i]);
                }
           
    if (end[i] <= end[i + 1] && start[i] >= start[i + 1])
                {        timespan = (end[i + 1] - start[i + 1]);
                }

                timeDifference = timespan.Days + timeDifference;

            }
                MessageBox.Show(timeDifference.ToString());

            }

        }
    }