How can I convert date-time value from Json to Gson

Question

I want to convert this json value to gson value. I'm able to get most of the data, the only place i'm getting stuck is field "time". Can anyone help me out, Please.

"quantity_map": {
    "https://example.com/abc/500/": {
        "available": 4,
        "requested": 1,
        "max": 4,
        "id": "500",
        "amount": {
            "2015-12-02": 3000.0,
            "2015-12-01": 3000.0,
            "2015-11-30": 3000.0
        },
        "time": "2015-11-27 11:46:38.612147+00:00"
    },
    "https://example.com/abc/499/": {
        "available": 5,
        "requested": 1,
        "max": 5,
        "id": "499",
        "amount": {
            "2015-12-02": 5500.0,
            "2015-12-01": 5500.0,
            "2015-11-30": 5500.0
        },
        "time": "2015-11-27 11:46:38.621023+00:00"
    }
}

Json to gson conversion code

for (Map.Entry<String, Object> mapEntry : quantityMap.entrySet()) {
                final String key = mapEntry.getKey();
                Log.d(TAG, mapEntry.getValue().toString());
                ConversionClass value = new ConversionClass();
                try {
                    value = new GsonBuilder()
                            .setDateFormat("yyyy-mm-dd hh:mm:ss.ssssssZ")
                            .create()
                            .fromJson(mapEntry.getValue().toString(), ConversionClass.class);
                } catch (Exception e) {
                    e.printStackTrace();
                }
            }

ConversionClass.class

public class ConversionClass{

private int available;
private int requested;
private int max;
private int id;
private HashMap<String, String> amount = new HashMap<>();
private Date time;

public void setAvailable(int available) {
    this.available = available;
}

public void setRequested(int requested) {
    this.requested = requested;
}

public void setMax(int max) {
    this.max = max;
}

public void setId(int id) {
    this.id = id;
}

public void setAmount(HashMap<String, String> amount) {
    this.amount = amount;
}

public void setTime(Date time) {
    this.time = time;
}

public int getAvailable() {
    return available;
}

public int getRequested() {
    return requested;
}

public int getMax() {
    return max;
}

public int getId() {
    return id;
}

public HashMap<String, String> getAmount() {
    return amount;
}

public Date getTime() {
    return time;
}
}