Improved error message

Author: jiachen1120

src/main/java/com/networknt/schema/DateTimeValidator.java

@@ -56,7 +56,7 @@ public Set<ValidationMessage> validate(JsonNode node, JsonNode rootNode, String
             return errors;
         }
         if (!isLegalDateTime(node.textValue())) {
-            errors.add(buildValidationMessage(at, node.textValue()));
+            errors.add(buildValidationMessage(at, node.textValue(), formatName));
         }
         return Collections.unmodifiableSet(errors);
     }

src/main/java/com/networknt/schema/ValidatorTypeCode.java

@@ -63,7 +63,7 @@ public JsonValidator newValidator(String schemaPath, JsonNode schemaNode, JsonSc
     TYPE("type", "1029", new MessageFormat("{0}: {1} found, {2} expected")),
     UNION_TYPE("unionType", "1030", new MessageFormat("{0}: {1} found, but {2} is required")),
     UNIQUE_ITEMS("uniqueItems", "1031", new MessageFormat("{0}: the items in the array must be unique")),
-    DATETIME("date-time", "1034", new MessageFormat("{0}: {1} is an invalid date/time"));
+    DATETIME("date-time", "1034", new MessageFormat("{0}: {1} is an invalid {2}"));
 
 	private static Map<String, ValidatorTypeCode> constants = new HashMap<String, ValidatorTypeCode>();