@Test
    public void timeToJson() {
        GregorianCalendar calendar = new GregorianCalendar(1970, Calendar.JANUARY, 1, 0, 0, 0);
        calendar.setTimeZone(TimeZone.getTimeZone("UTC"));
        calendar.add(Calendar.MILLISECOND, 14400000);
        java.util.Date date = calendar.getTime();

        JsonNode converted = parse(converter.fromConnectData(TOPIC, Time.SCHEMA, date));
        validateEnvelope(converted);
        assertEquals(parse("{ \"type\": \"int32\", \"optional\": false, \"name\": \"org.apache.kafka.connect.data.Time\", \"version\": 1 }"),
                converted.get(JsonSchema.ENVELOPE_SCHEMA_FIELD_NAME));
        JsonNode payload = converted.get(JsonSchema.ENVELOPE_PAYLOAD_FIELD_NAME);
        assertTrue(payload.isInt());
        assertEquals(14400000, payload.longValue());
    }
When schemas are disabled, fields are mapped to Connect maps.
connect/json/src/test/java/org/apache/kafka/connect/json/JsonConverterTest.java