diff --git a/Main.java b/Main.java
index c99d7f5..cef4a95 100644
--- a/Main.java
+++ b/Main.java
@@ -3,14 +3,114 @@
  *  Last edited : 5/31/2016
  */
 
+import java.util.Date
+
 class Main
 {
   Exception BookNotFound = new Exception("Error 404 : Book not found");
   static BookFactory books = new BookFactory();
+  static UserFactory users = new UserFactory();
+  static Date date = new Date();
 
   public static void main(String[] args)
   {
 
   }
 
+  public static boolean returnBook(User user, Book book)
+  {
+    User newUser = user;
+
+    if(newUser.returnBook(book.getId()))
+    {
+      book.returned();
+
+      books.update(book);
+      users.update(user, newUser);
+
+      return true;
+    }
+
+    return false;
+  }
+
+  public static int[] calDueDate(int days)
+  {
+    int[] dueDate = currentDay();
+
+    for (int i = 0; i < days; i++)
+    {
+      if(dueDate[2] < 28)
+      {
+        dueDate[2]++;
+      }
+      else if(dueDate[1] == 12)
+      {
+        if(dueDate[2] == 31)
+        {
+          dueDate[0]++;
+          dueDate[1] = 1;
+          dueDate[2] = 1;
+        }
+      }
+      else if(dueDate[1] == 2)
+      {
+        if((dueDate[0] % 4) == 0)
+        {
+          if(dueDate[2] == 29)
+          {
+            dueDate[1]++;
+            dueDate[2] = 1;
+          }
+          else
+          {
+            dueDate[2]++;
+          }
+        }
+        else if(dueDate[2] == 28)
+        {
+          dueDate[1]++;
+          dueDate[2] = 1;
+        }
+        else
+        {
+          dueDate[2]++;
+        }
+      }
+      else if(dueDate[1] == 4 || dueDate[1] == 6 || dueDate[1] == 9 || dueDate[1] == 11)
+      {
+        if(dueDate[2] == 30)
+        {
+          dueDate[1]++;
+          dueDate[2] = 1;
+        }
+        else
+        {
+          dueDate[2]++;
+        }
+      }
+      else if(dueDate[2] == 31)
+      {
+        dueDate[1]++;
+        dueDate[2] = 1;
+      }
+      else
+      {
+        dueDate[2]++;
+      }
+    }
+
+    return dueDate;
+  }
+
+  public static int[] currentDay()
+  {
+    int[] currentDay = new int[3]();
+
+    currentDay[0] = date.getYear();
+    currentDay[1] = date.getMonth();
+    currentDay[2] = date.getDate();
+
+    return currentDay;
+  }
 }