diff --git a/src/core/CMakeLists.txt b/src/core/CMakeLists.txt
index 79057d2..e238864 100644
--- a/src/core/CMakeLists.txt
+++ b/src/core/CMakeLists.txt
@@ -1,6 +1,6 @@
 
 
-find_package(Boost 1.62 REQUIRED)
+find_package(Boost 1.62 COMPONENTS date_time REQUIRED)
 find_package(SQLite3 REQUIRED)
 
 #set(CORE_HEADERS
@@ -13,8 +13,9 @@ set(CORE_SOURCES
     entity.cpp
     seller.cpp
     article.cpp
+    sale.cpp
 )
 
 add_library(core STATIC ${CORE_SOURCES})
-target_link_libraries(core Boost::boost)
+target_link_libraries(core Boost::boost Boost::date_time)
 target_link_libraries(core sqlite3)
\ No newline at end of file
diff --git a/src/core/article.cpp b/src/core/article.cpp
index b56c413..b798fbb 100644
--- a/src/core/article.cpp
+++ b/src/core/article.cpp
@@ -16,4 +16,6 @@ bool Article::isSold() { return salePtr_ ? true : false; }
 
 std::string Article::getDescription() { return description_; }
 
-Seller* Article::getSeller() { return sellerPtr_.get(); }
\ No newline at end of file
+Seller* Article::getSeller() { return sellerPtr_.get(); }
+
+int Article::getPrice() { return price_; }
\ No newline at end of file
diff --git a/src/core/article.h b/src/core/article.h
index 4042924..03ceaf0 100644
--- a/src/core/article.h
+++ b/src/core/article.h
@@ -9,6 +9,7 @@
 #include <string>
 
 class Seller;
+class Sale;
 
 class Article : public Entity
 {
@@ -24,6 +25,7 @@ class Article : public Entity
 
     std::string getDescription();
     Seller* getSeller();
+    int getPrice();
 
   private:
     std::shared_ptr<Seller> sellerPtr_{};
diff --git a/src/core/database.cpp b/src/core/database.cpp
index 086dfc9..bec8d37 100644
--- a/src/core/database.cpp
+++ b/src/core/database.cpp
@@ -184,7 +184,7 @@ unsigned int Database::storeSellers(std::vector<Seller>& sellers)
                 sqlite3_finalize(stmt);
                 throw std::runtime_error(errMsg);
             }
-            seller.setState(Seller::State::CLEAN);
+            seller.setState(Seller::State::OK);
             ++count;
             sqlite3_finalize(stmt);
         }
diff --git a/src/core/entity.h b/src/core/entity.h
index 786d393..8f1f63f 100644
--- a/src/core/entity.h
+++ b/src/core/entity.h
@@ -9,7 +9,7 @@
 class Entity
 {
   public:
-    enum class State { NEW, UPDATED, CLEAN };
+    enum class State { NEW, UPDATE, DELETE, OK };
 
     virtual ~Entity() = 0;
     const boost::uuids::uuid& getUuid() const { return uuid_; };
diff --git a/src/core/sale.cpp b/src/core/sale.cpp
new file mode 100644
index 0000000..8407232
--- /dev/null
+++ b/src/core/sale.cpp
@@ -0,0 +1,10 @@
+#include "sale.h"
+
+#include <numeric>
+
+int Sale::sumInCents()
+{
+    int test = std::accumulate(articles_.begin(), articles_.end(), 0,
+                               [](int a, Article* b) { return a + b->getPrice(); });
+    return test;
+}
\ No newline at end of file
diff --git a/src/core/sale.h b/src/core/sale.h
index 06f350d..e4d016e 100644
--- a/src/core/sale.h
+++ b/src/core/sale.h
@@ -1,8 +1,21 @@
 #ifndef SALE_H
 #define SALE_H
 
-class Sale : public Entity {
+#include "article.h"
 
+#include <vector>
+
+#include <boost/date_time.hpp>
+
+class Article;
+
+class Sale : public Entity
+{
+  public:
+    int sumInCents();
+  private:
+    boost::posix_time::ptime systemTime_{boost::posix_time::second_clock::local_time()};
+    std::vector<Article*> articles_{};
 };
 
 #endif
\ No newline at end of file
diff --git a/test/test_database.cpp b/test/test_database.cpp
index b2b4bf3..e4052c4 100644
--- a/test/test_database.cpp
+++ b/test/test_database.cpp
@@ -51,6 +51,6 @@ BOOST_AUTO_TEST_CASE(seller_states)
     std::cout << "Anzahl sellers: " << sellers.size() << "\n";
     BOOST_TEST((sellers.at(0).getState() == Entity::State::NEW));
     BOOST_TEST(db.storeSellers(sellers) == 1);
-    BOOST_TEST((sellers.at(0).getState() == Entity::State::CLEAN));
+    BOOST_TEST((sellers.at(0).getState() == Entity::State::OK));
     BOOST_TEST(db.storeSellers(sellers) == 0);
 }
\ No newline at end of file
diff --git a/test/test_seller.cpp b/test/test_seller.cpp
index b389820..2c0468f 100644
--- a/test/test_seller.cpp
+++ b/test/test_seller.cpp
@@ -35,4 +35,5 @@ BOOST_AUTO_TEST_CASE(with_article) {
     article->setDescription("Test article");
     seller.addArticle(article);
     BOOST_TEST(seller.getArticles().at(0)->getDescription() == "Test article");
+    BOOST_TEST(seller.soldArticles() == 0);
 }
\ No newline at end of file