Deserialise Json Timestamp with System.Text.Json

Question

I am trying to deserialise the following JSON

{"serverTime":1613967667240}

into an object of the following class

public class ApiServerTime
{
    [JsonPropertyName("serverTime")]
    public DateTime ServerTime
    {
        get;
        private set;
    }
}

with the following command:

JsonSerializer.Deserialize<ApiServerTime>(jsonString);

but the resulting object contains the ServerTime == DateTime.MinValue. What am I doing wrong?

Does this answer your question? [How to deserialize a unix timestamp (μs) to a DateTime from JSON?](https://stackoverflow.com/questions/19971494/how-to-deserialize-a-unix-timestamp-%ce%bcs-to-a-datetime-from-json) — KennetsuR, Feb 22 '21 at 05:47
@KenTsu I found that but it's related to Newtonsoft.Json. I am using System.Text.Json — Benj, Feb 22 '21 at 05:50

score 5 · Accepted Answer · answered Feb 22 '21 at 08:32

You can register custom date formatters for System.Text.Json also. https://learn.microsoft.com/en-us/dotnet/standard/datetime/system-text-json-support

public class DateTimeConverterForCustomStandardFormatR : JsonConverter<DateTime>
{
    public override DateTime Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        return DateTime.UnixEpoch.AddMilliseconds(reader.GetInt64());
    }

    public override void Write(Utf8JsonWriter writer, DateTime value, JsonSerializerOptions options)
    {
        // The "R" standard format will always be 29 bytes.
        Span<byte> utf8Date = new byte[29];

        bool result = Utf8Formatter.TryFormat(value, utf8Date, out _, new StandardFormat('R'));
        Debug.Assert(result);

        writer.WriteStringValue(utf8Date);
    }
}


string js = "{\"ServerTime\":1613967667240}";
JsonSerializerOptions options = new JsonSerializerOptions();
options.Converters.Add(new DateTimeConverterForCustomStandardFormatR());
var value = JsonSerializer.Deserialize<ApiServerTime>(js, options);

stoj · Answer 2 · 2023-02-23T14:37:13.193

In the spirit of building a better mouse trap, here's an implementation that supports..

Unix time in seconds OR milliseconds based on whether the value in seconds can represented within .net DateTime min/max range (1/1/0001 to 31/12/9999).
Nullable DateTime to gracefully cater for invalid, empty, and null values.

public class UnixToNullableDateTimeConverter : JsonConverter<DateTime?>
{
    public bool? IsFormatInSeconds { get; init; }

    public override DateTime? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
    {
        try
        {
            if (reader.TryGetInt64(out var time))
            {
                // if 'IsFormatInSeconds' is unspecified, then deduce the correct type based on whether it can be represented as seconds within the .net DateTime min/max range (1/1/0001 to 31/12/9999)
                // - because we're dealing with a 64bit value, the unix time in seconds can exceed the traditional 32bit min/max restrictions (1/1/1970 to 19/1/2038)
                if (IsFormatInSeconds == true || IsFormatInSeconds == null && time > _unixMinSeconds && time < _unixMaxSeconds)
                    return DateTimeOffset.FromUnixTimeSeconds(time).LocalDateTime;
                return DateTimeOffset.FromUnixTimeMilliseconds(time).LocalDateTime;
            }
        }
        catch
        {
            // despite the method prefix 'Try', TryGetInt64 will throw an exception if the token isn't a number.. hence we swallow it and return null
        }
        
        return null;
    }

    // write is out of scope, but this could be implemented via writer.ToUnixTimeMilliseconds/WriteNullValue
    public override void Write(Utf8JsonWriter writer, DateTime? value, JsonSerializerOptions options) => throw new NotSupportedException();

    private static readonly long _unixMinSeconds = DateTimeOffset.MinValue.ToUnixTimeSeconds(); // -62_135_596_800
    private static readonly long _unixMaxSeconds = DateTimeOffset.MaxValue.ToUnixTimeSeconds(); // 253_402_300_799
}

KennetsuR · Answer 3 · 2021-02-22T07:27:11.000

according to What is the “right” JSON date format? you had better to use ISO 8601

"\"\\/Date(1335205592410)\\/\""         .NET JavaScriptSerializer
"\"\\/Date(1335205592410-0500)\\/\""    .NET DataContractJsonSerializer
"2012-04-23T18:25:43.511Z"              JavaScript built-in JSON object
"2012-04-21T18:25:43-05:00"             ISO 8601

you also can use JsonMicrosoftDateTimeConverter to deserialize it. but it need change json presentation. your can reference the link System.Text.Json DateTime & DateTimeOffset “/Date()/” serialization

{
    "Date": "\/Date(1580803200000-0800)\/"
}

at last, you can use temporary model to save current timestamp, then convert it.

public class ApiServerTime{
public long ServerTime{get;set;}
public static DateTime UnixTimeStampToDateTime( double unixTimeStamp )
{
    // Unix timestamp is seconds past epoch
    System.DateTime dtDateTime = new DateTime(1970,1,1,0,0,0,0,System.DateTimeKind.Utc);
    dtDateTime = dtDateTime.AddSeconds( unixTimeStamp ).ToLocalTime();
    return dtDateTime;
}
}

Deserialise Json Timestamp with System.Text.Json

3 Answers3