diff --git a/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyDefaultTimezoneUnitTest.java b/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyDefaultTimezoneUnitTest.java
new file mode 100644
index 0000000000..05d36d2c6c
--- /dev/null
+++ b/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyDefaultTimezoneUnitTest.java
@@ -0,0 +1,22 @@
+package com.baeldung.timezone;
+
+import org.junit.Test;
+
+import java.util.Calendar;
+import java.util.Date;
+import java.util.TimeZone;
+
+import static org.junit.Assert.assertEquals;
+
+public class ModifyDefaultTimezoneUnitTest {
+
+    @Test
+    public void givenDefaultTimezoneSet_thenDateTimezoneIsCorrect() {
+        TimeZone.setDefault(TimeZone.getTimeZone("Portugal"));
+        Date date = new Date();
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+        assertEquals(calendar.getTimeZone(), TimeZone.getTimeZone("Portugal"));
+    }
+
+}
diff --git a/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyTimezonePropertyUnitTest.java b/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyTimezonePropertyUnitTest.java
new file mode 100644
index 0000000000..8f65f520f8
--- /dev/null
+++ b/core-java-modules/core-java-date-operations/src/test/java/com/baeldung/timezone/ModifyTimezonePropertyUnitTest.java
@@ -0,0 +1,34 @@
+package com.baeldung.timezone;
+
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Calendar;
+import java.util.Date;
+import java.util.TimeZone;
+
+import static org.junit.Assert.assertEquals;
+
+public class ModifyTimezonePropertyUnitTest {
+
+    @Before
+    public void setup() {
+        System.setProperty("user.timezone", "IST");
+        TimeZone.setDefault(null);
+    }
+
+    @After
+    public void teardown() {
+        System.clearProperty("user.timezone");
+    }
+
+    @Test
+    public void givenTimezonePropertySet_thenDateTimezoneIsCorrect() {
+        Date date = new Date();
+        Calendar calendar = Calendar.getInstance();
+        calendar.setTime(date);
+        assertEquals(calendar.getTimeZone(), TimeZone.getTimeZone("IST"));
+    }
+
+}
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