Question: ```
Java.util.Date
startDate : 2020-07-13 09:00:00.0

```

// JSON response

```
"startDate" : 1594611000000

```

I want to display in JSON as 2020-07-13 09:00:00.0

Answer: 
If the POJO object used for serialization/deserialization has a Date field, something like below, it should be informed to the library (say, Jackson ) which is used for serializing/deserializing.

```
class JsonTest{
  private Date date;
}

```

When the serialization/deserialization is performed, the details of the data format is to be set with the Serializer/ DeSerializer. Sample Deserialization code using Jackson (using com.fasterxml.jackson.core) can be

```
public static void main(String[] args) throws JsonProcessingException, ParseException 

{
        //2020-07-13 09:00:00.0
        SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss.S");
        String dateString = format.format( new Date()   );
        Date   date       = format.parse ( "2020-07-13 09:00:00.0" );
        JsonTest jsonTest = new JsonTest();
        jsonTest.setDate(date);
        ObjectMapper mapper = new ObjectMapper();

        //mapper should know that the  specific format is needed while conversion 
        mapper.setDateFormat(format);
        mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);

        System.out.println(mapper.writeValueAsString(jsonTest));

    }

```

The output will be printed as

```
{"date":"2020-07-13 09:00:00.0"}

```
You mention that your variable startDate is of Date type, now i don't know what language you are using but i can try an educated guess of what you need to do :

Format you Date type in order to have a String type and put that String in your JSON. Being a String and not the interpretation of a Timestamp, is shouldn't be converted.