Examples: use {{ site.time | date: "%Y" }}.

Since they are being build, no point in hardcoding the year.

site/docs/4.2/examples/floating-labels/index.html

@@ -28,5 +28,5 @@ include_js: false
     </label>
   </div>
   <button class="btn btn-lg btn-primary btn-block" type="submit">Sign in</button>
-  <p class="mt-5 mb-3 text-muted text-center">&copy; 2017-2019</p>
+  <p class="mt-5 mb-3 text-muted text-center">&copy; 2017-{{ site.time | date: "%Y" }}</p>
 </form>