diff --git a/OCPP-J/src/main/java/eu/chargetime/ocpp/JSONCommunicator.java b/OCPP-J/src/main/java/eu/chargetime/ocpp/JSONCommunicator.java
index 15e937d0..01f3147f 100644
--- a/OCPP-J/src/main/java/eu/chargetime/ocpp/JSONCommunicator.java
+++ b/OCPP-J/src/main/java/eu/chargetime/ocpp/JSONCommunicator.java
@@ -9,6 +9,8 @@
 import java.lang.reflect.Type;
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
+import java.time.format.DateTimeFormatterBuilder;
+import java.time.format.ResolverStyle;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
@@ -46,6 +48,16 @@ public class JSONCommunicator extends Communicator {
 
   private static final Logger logger = LoggerFactory.getLogger(JSONCommunicator.class);
 
+  /**
+   * a derivation of ISO_INSTANT that always serializes to three millisecond digits, even if zero
+   */
+  public static final DateTimeFormatter ISO_INSTANT_WITH_MILLIS_PRECISION =
+      new DateTimeFormatterBuilder()
+          .parseCaseInsensitive()
+          .appendInstant(3)
+          .toFormatter()
+          .withResolverStyle(ResolverStyle.STRICT);
+
   private static final int INDEX_MESSAGEID = 0;
   private static final int TYPENUMBER_CALL = 2;
   private static final int INDEX_CALL_ACTION = 2;
@@ -94,7 +106,7 @@ private static class ZonedDateTimeSerializer
     @Override
     public JsonElement serialize(
         ZonedDateTime zonedDateTime, Type type, JsonSerializationContext jsonSerializationContext) {
-      return new JsonPrimitive(zonedDateTime.format(DateTimeFormatter.ISO_INSTANT));
+      return new JsonPrimitive(zonedDateTime.format(ISO_INSTANT_WITH_MILLIS_PRECISION));
     }
 
     @Override
diff --git a/ocpp-v1_6/src/test/java/eu/chargetime/ocpp/test/JSONCommunicatorTest.java b/ocpp-v1_6/src/test/java/eu/chargetime/ocpp/test/JSONCommunicatorTest.java
index 0436cf22..da2b4b70 100644
--- a/ocpp-v1_6/src/test/java/eu/chargetime/ocpp/test/JSONCommunicatorTest.java
+++ b/ocpp-v1_6/src/test/java/eu/chargetime/ocpp/test/JSONCommunicatorTest.java
@@ -102,6 +102,22 @@ public void unpackPayload_aCalendarPayload_returnsTestModelWithACalendar() throw
     assertThat(model.getCalendarTest().compareTo(someDate), is(0));
   }
 
+  @Test
+  public void unpackPayload_aCalendarPayload_parsesNoFractionalAsZeroFractional() throws Exception {
+    // Given
+    String aCalendar = "2016-04-28T07:16:11Z";
+    String payload = "{\"calendarTest\":\"%s\"}";
+
+    ZonedDateTime someDate = ZonedDateTime.parse("2016-04-28T07:16:11.000Z");
+
+    // When
+    TestModel model =
+        communicator.unpackPayload(String.format(payload, aCalendar), TestModel.class);
+
+    // Then
+    assertThat(model.getCalendarTest().compareTo(someDate), is(0));
+  }
+
   @Test
   public void unpackPayload_anIntegerPayload_returnsTestModelWithAnInteger() throws Exception {
     // Given
@@ -276,6 +292,24 @@ public void pack_bootNotificationRequest_returnsBootNotificationRequestPayload()
     assertThat(payload, equalTo(expected));
   }
 
+  @Test
+  public void pack_bootNotificationConfirmation_limitsTimeFractionalDigitsToThree()
+      throws Exception {
+    // Given
+    String expected =
+        "{\"currentTime\":\"2016-04-28T06:41:13.123Z\",\"interval\":300,\"status\":\"Accepted\"}";
+    BootNotificationConfirmation confirmation = new BootNotificationConfirmation();
+    confirmation.setCurrentTime(createDateTimeInNanos(1461825673123456789L)); // will be truncated
+    confirmation.setInterval(300);
+    confirmation.setStatus(RegistrationStatus.Accepted);
+
+    // When
+    Object payload = communicator.packPayload(confirmation);
+
+    // Then
+    assertThat(payload, equalTo(expected));
+  }
+
   @Test
   public void pack_bootNotificationConfirmation_returnsBootNotificationConfirmationPayload()
       throws Exception {
@@ -294,6 +328,24 @@ public void pack_bootNotificationConfirmation_returnsBootNotificationConfirmatio
     assertThat(payload, equalTo(expected));
   }
 
+  @Test
+  public void pack_bootNotificationConfirmation_alwaysFormatsTimeWithThreeFractionalDigits()
+      throws Exception {
+    // Given
+    String expected =
+        "{\"currentTime\":\"2016-04-28T06:41:13.000Z\",\"interval\":300,\"status\":\"Accepted\"}";
+    BootNotificationConfirmation confirmation = new BootNotificationConfirmation();
+    confirmation.setCurrentTime(createDateTimeInMillis(1461825673000L)); // will not be truncated
+    confirmation.setInterval(300);
+    confirmation.setStatus(RegistrationStatus.Accepted);
+
+    // When
+    Object payload = communicator.packPayload(confirmation);
+
+    // Then
+    assertThat(payload, equalTo(expected));
+  }
+
   @Test
   public void disconnect_disconnects() {
     // When
@@ -319,4 +371,9 @@ public void sendError_transmitsError() throws Exception {
   private ZonedDateTime createDateTimeInMillis(long dateInMillis) {
     return Instant.ofEpochMilli(dateInMillis).atOffset(ZoneOffset.UTC).toZonedDateTime();
   }
+
+  private ZonedDateTime createDateTimeInNanos(long dateInNanos) {
+    return Instant.ofEpochSecond(dateInNanos / 1000000000, dateInNanos % 1000000000)
+        .atOffset(ZoneOffset.UTC).toZonedDateTime();
+  }
 }