[BAEL-3315] Added missing code snippets from the Java 8 Date/Time article

Also:
- formatted changed files with Eclipse profile
- corrected failing test: givenTwoDatesInJava8_whenDifferentiating_thenWeGetSix

java-dates/src/test/java/com/baeldung/datetime/UseToInstantUnitTest.java

@@ -0,0 +1,33 @@
+package com.baeldung.datetime;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import java.time.LocalDateTime;
+import java.util.Calendar;
+import java.util.Date;
+import java.util.GregorianCalendar;
+
+import org.junit.Test;
+
+public class UseToInstantUnitTest {
+
+    private UseToInstant subject = new UseToInstant();
+
+    @Test
+    public void givenAGregorianCalenderDate_whenConvertingToLocalDate_thenAsExpected() {
+        GregorianCalendar givenCalender = new GregorianCalendar(2018, Calendar.JULY, 28);
+
+        LocalDateTime localDateTime = subject.convertDateToLocalDate(givenCalender);
+
+        assertThat(localDateTime).isEqualTo("2018-07-28T00:00:00");
+    }
+
+    @Test
+    public void givenADate_whenConvertingToLocalDate_thenAsExpected() {
+        Date givenDate = new Date(1465817690000L);
+
+        LocalDateTime localDateTime = subject.convertDateToLocalDate(givenDate);
+
+        assertThat(localDateTime).isEqualTo("2016-06-13T13:34:50");
+    }
+}