diff --git a/apps/chapter_05.cpp b/apps/chapter_05.cpp
index f3cfdbe..343cd01 100644
--- a/apps/chapter_05.cpp
+++ b/apps/chapter_05.cpp
@@ -26,6 +26,7 @@
 // This is an independent project of an individual developer. Dear PVS-Studio, please check it.
 // PVS-Studio Static Code Analyzer for C, C++, C#, and Java: http://www.viva64.com
 
+#include <chrono>
 #include <cstdio>
 
 #include <raytracing.h>
@@ -37,6 +38,7 @@
 #define kWallZ     10
 
 using namespace Raytracer;
+using namespace std;
 
 /* ------------------------------------------------------------------------- */
 
@@ -86,6 +88,17 @@ int shadow_sphere(uint8_t a_canvas_pixels, double a_wall_size, uint8_t a_wall_z)
 
 int main(void)
 {
+    int the_ret;
+    chrono::time_point<chrono::high_resolution_clock> the_start, the_end;
+
     printf("Chapter 05 example.\n");
-    return shadow_sphere(kImageSize, kWallSize, kWallZ);
+
+    the_start = chrono::high_resolution_clock::now();
+    the_ret   = shadow_sphere(kImageSize, kWallSize, kWallZ);
+    the_end   = chrono::high_resolution_clock::now();
+
+    chrono::duration<double> the_elapsed_time = the_end - the_start;
+    printf("Execution Time: %f secondes\n", the_elapsed_time.count());
+
+    return the_ret;
 }
diff --git a/apps/chapter_06.cpp b/apps/chapter_06.cpp
index b94e817..9bb290e 100644
--- a/apps/chapter_06.cpp
+++ b/apps/chapter_06.cpp
@@ -26,6 +26,7 @@
 // This is an independent project of an individual developer. Dear PVS-Studio, please check it.
 // PVS-Studio Static Code Analyzer for C, C++, C#, and Java: http://www.viva64.com
 
+#include <chrono>
 #include <cstdio>
 
 #include <raytracing.h>
@@ -37,6 +38,7 @@
 #define kWallZ     10
 
 using namespace Raytracer;
+using namespace std;
 
 /* ------------------------------------------------------------------------- */
 
@@ -93,6 +95,17 @@ int shadow_sphere(uint8_t a_canvas_pixels, double a_wall_size, uint8_t a_wall_z)
 
 int main(void)
 {
+    int the_ret;
+    chrono::time_point<chrono::high_resolution_clock> the_start, the_end;
+
     printf("Chapter 06 example.\n");
-    return shadow_sphere(kImageSize, kWallSize, kWallZ);
+
+    the_start = chrono::high_resolution_clock::now();
+    the_ret   = shadow_sphere(kImageSize, kWallSize, kWallZ);
+    the_end   = chrono::high_resolution_clock::now();
+
+    chrono::duration<double> the_elapsed_time = the_end - the_start;
+    printf("Execution Time: %f secondes\n", the_elapsed_time.count());
+
+    return the_ret;
 }
diff --git a/apps/chapter_07.cpp b/apps/chapter_07.cpp
index 17e97d0..f256e75 100644
--- a/apps/chapter_07.cpp
+++ b/apps/chapter_07.cpp
@@ -26,6 +26,7 @@
 // This is an independent project of an individual developer. Dear PVS-Studio, please check it.
 // PVS-Studio Static Code Analyzer for C, C++, C#, and Java: http://www.viva64.com
 
+#include <chrono>
 #include <cstdio>
 
 #include <raytracing.h>
@@ -33,6 +34,7 @@
 /* ------------------------------------------------------------------------- */
 
 using namespace Raytracer;
+using namespace std;
 
 /* ------------------------------------------------------------------------- */
 
@@ -43,6 +45,8 @@ int main(void)
     Canvas the_canvas;
     Sphere *the_floor, *the_left_wall, *the_right_wall;
     Sphere *the_middle, *the_right, *the_left;
+    chrono::time_point<chrono::high_resolution_clock> the_start, the_end;
+
     printf("Chapter 07 example.\n");
 
     // Floor is an extremely flattened sphere with a matte texture.
@@ -100,9 +104,14 @@ int main(void)
     the_camera.set_transform(
         Matrix::view_transform(Tuple::Point(0, 1.5, -5), Tuple::Point(0, 1, 0), Tuple::Vector(0, 1, 0)));
 
+    the_start  = chrono::high_resolution_clock::now();
     the_canvas = the_camera.render(the_world);
+    the_end    = chrono::high_resolution_clock::now();
 
     the_canvas.save_to_file("chapter07.ppm");
 
+    chrono::duration<double> the_elapsed_time = the_end - the_start;
+    printf("Execution Time: %f secondes\n", the_elapsed_time.count());
+
     return 0;
 }