Unity Json utility does not serialize DateTime

Question

Like the title said the unity json utility does not seem to allow me to serialize the DateTime structure. Just to clarify the problem is that I'm serializing this class:

[Serializable]
public class SaveData {

public Vector3 playerPosition;
public Quaternion playerRot;
public List<Item> inventory;

public DateTime saveTime;

public int playerHealth;

public int strength;
public int attack;
public int defense;
public int agility;

}

When I actually write to the json file I get everything but the DateTime and no errors. This is the result:

{
"playerPosition": {
    "x": -142.27000427246095,
    "y": -7.000000476837158,
    "z": -112.80999755859375
},
"playerRot": {
    "x": 0.0,
    "y": 0.0,
    "z": 0.0,
    "w": 1.0
},
"inventory": [],
"playerHealth": 100,
"strength": 0,
"attack": 0,
"defense": 0,
"agility": 0
}

Is there a way around this?

A little update to this question so that I can show another way I've worked around this problem if the answer below isn't for you.

I was recently working on a similar problem and solved it by doing the follow:

I created a new class called "NewDateTime":

[System.Serializable]
public class NewDateTime {
public int second;
public int minute;
public int hour;

public int day;
public int month;
public int year;

public NewDateTime CreateNewDateTime(DateTime dateTime) {
    NewDateTime newDateTime = new NewDateTime();
    newDateTime.second = dateTime.Second;
    newDateTime.minute = dateTime.Minute;
    newDateTime.hour = dateTime.Hour;
    newDateTime.day = dateTime.Day;
    newDateTime.month = dateTime.Month;
    newDateTime.year = dateTime.Year;

    return newDateTime;
}

public override string ToString() {
    return day + "/" + month + "/" + year + " at " + hour + ":" + minute + ":" + second;
}}

and then for example when I want to save the date to json I would do something like the following:

saveDateTime = newDateTime.CreateNewDateTime(DateTime.Now)

it's a rather simple workaround but I thought it might help.

More details? How's it working now? What are you expecting it to do? — House
– House, Commented Feb 17, 2017 at 23:06
I wish to use it to save the time when the player saves the game. I have the same system working. Everything else within the class which is being serialized is saving to the Json file apart from the DateTime. — Yatoniea
– Yatoniea, Commented Feb 17, 2017 at 23:21
Yeah. So it's just missing from the resulting JSON? There's no errors? Is the field public? Technical details please. — House
– House, Commented Feb 17, 2017 at 23:24
Oh, sorry yes it is just missing the resulting json and no errors whatsoever. — Yatoniea
– Yatoniea, Commented Feb 17, 2017 at 23:25

IAmHello · Accepted Answer · 2021-11-11 13:41:42Z

The problem with JsonUtility, is that it doesn't save properties, just public fields and fields with the [SerializeField] attribute.

You can solve this with another class and some conversion magic, like so:

Json Serializable Class

[Serializable]
struct JsonDateTime {
    public long value;
    public static implicit operator DateTime(JsonDateTime jdt) {
        Debug.Log("Converted to time");
        return DateTime.FromFileTimeUtc(jdt.value);
    }
    public static implicit operator JsonDateTime(DateTime dt) {
        Debug.Log("Converted to JDT");
        JsonDateTime jdt = new JsonDateTime();
        jdt.value = dt.ToFileTimeUtc();
        return jdt;
    }
}

Usage example

var time = DateTime.Now;
print(time);
var json = JsonUtility.ToJson((JsonDateTime) time);
print(json);
DateTime timeFromJson = JsonUtility.FromJson<JsonDateTime>(json);
print(timeFromJson);

Output

DMGregory · Accepted Answer · 2022-02-20 23:12:33Z

2

As it happens, I was just working on a telemetry example for my students, where I used this approach:

[SerializeField] long _timecode;
public DateTimeOffset time {
    get {
        return DateTimeOffset.FromUnixTimeMilliseconds(_timecode);
    }
    set {
        _timecode = value.ToUnixTimeMilliseconds();
    }
}

This way the serialized form is just a simple 64-bit integer, while consuming code can read/write it using the richer DateTimeOffset API. In my case, using the Unix time convention helped ensure I'd get consistent behaviour between my Unity game and a Node.js server.

Anytime I needed the current moment, I'd capture it as data.time = System.DateTimeOffset.UtcNow;

answered Feb 20, 2022 at 23:12

DMGregory♦

141k23 gold badges257 silver badges401 bronze badges

\$\begingroup\$ Smart solution. Works excellent. \$\endgroup\$

ow3n
– ow3n

2025-07-10 19:55:08 +00:00
Commented Jul 10 at 19:55

Add a comment |

Indrit Vaka · Accepted Answer · 2022-02-20 22:28:03Z

I just faced the same problem and I fixed that by using Newtonsoft instead of JsonUtility as a converter.

here is an example

//here we will serialise or deserialize the data

public void SaveData
{

        List<Model> models = new List<Model>();
        //just adding some data
        models.Add(new Model { playerHealth = 10, saveTime = DateTime.Now, strength = 50 });

        //here pasing the data that are stoed on that variable into a json format
        string jsonText = Newtonsoft.Json.JsonConvert.SerializeObject(models);
        Debug.Log(jsonText);
}

//this is the model

public class Model
{
    public DateTime saveTime;

    public int playerHealth;

    public int strength;

}

here are result

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