Instant incorrectly parsing epoch string with rest api

I have a rest API with an input value which is an epoch. However, storing as an Instant ignores the nanos, thus storing it as some date in the future (I think). I could be storing them in the wrong type also as had thought about storing them as a long either.

Example: From the input of 683124845000 I am expecting a date and time in 1991. It is converted to +23617-05-13T13:23:20Z.

public class Booking {
    private Instant epoch;
    private String email;
}

The JSON input is:

{
  "epoch": "683124845000", 
  "email": "email@email.com"
}

Currently, I just have a controller that returns OK regardless of input as I am modeling the input.

@PostMapping("/booking")
    public ResponseEntity createBooking(@RequestBody Booking booking) {
        return ResponseEntity.ok().build();
    }

The default Instant serializer is expecting the epoch to be in seconds. Here are the following solutions:

1. Use long or Long to store the epoch.
2. Change your API to expect seconds.
3. Create custom serializer / deserializer.

Custom serializer / deserializer implementation:
(Assuming you want to use milliseconds for your API since the epoch in the question seemed to be in milliseconds)

Serializer

public class CustomInstantSerializer extends JsonSerializer<Instant> {

    @Override
    public void serialize(Instant value, JsonGenerator gen, SerializerProvider serializers) throws IOException {
        long epoch = value.toEpochMilli();
        gen.writeNumber(epoch);
    }

}

Deserializer

public class CustomInstantDeserializer extends JsonDeserializer<Instant> {

    @Override
    public Instant deserialize(JsonParser jp, DeserializationContext ctxt) throws IOException {
        long epoch = jp.getLongValue();
        return Instant.ofEpochMilli(epoch);
    }

}

Then wiring the serializer / deserializer to the field:

public class Booking {

    @JsonSerialize(using = CustomInstantSerializer.class)
    @JsonDeserialize(using = CustomInstantDeserializer.class)
    private Instant epoch;

    private String email;

}