sesti zadatak:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Windows.Forms;

namespace WindowsFormsApplication33
{
    public partial class Form1 : Form
    {
        public Form1()
        {
            InitializeComponent();
        }
        public DateTime sutra(string datum)
        {
            DateTime vreme = Convert.ToDateTime(datum);
            DateTime sutra = vreme.AddDays(1);
            return sutra;

        }
        private void Form1_Load(object sender, EventArgs e)
        {

        }

        private void Form1_DoubleClick(object sender, EventArgs e)
        {
            string datum = textBox1.Text;
            textBox2.Text = sutra(datum).ToString();
        }
    }
}