DateTime.Parse does not handle string that conform to RFC 3339

[CoryCharlton]

Library/API/IoT binding

nanoFramework.CoreLibrary

Visual Studio version

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.NET nanoFramework extension version

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Target name(s)

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Firmware version

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Device capabilities

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Description

RFC 3339 does not specify the number of digits for the fractional second portion but a common practice is to use three digits so the fractional second portion relates to whole milliseconds:

yyyy-MM-dd'T'HH:mm:ss.fffK (or yyyy-MM-dd'T'HH:mm:ss.fffZ in NF since 'K' isn't supported and all DateTime are assumed to be UTC)

Ex: 2024-05-15T04:20:05.069Z

Unfortunately the DateTime.Parse implementation in NF is currently only supporting the ISO 8601 "round trip time" format which requires that the fractional second portion contain 7 digits (yyyy-MM-ddTHH:mm:ss.fffffff) code.

This causes the example string above to parse with '0' milliseconds and '69' "extra" ticks. The issue is here because the code assumes the string represents a 7 digit number '0000069' when the correct 7 digit number is '0690000'

How to reproduce

See sample code below.

Expected behaviour

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Screenshots

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Sample project or code

var dateTime1 = new DateTime(2024, 5, 15, 4, 20, 5, 69);
var dateTimeString = dateTime1.ToString("yyyy-MM-dd'T'HH:mm:ss.fffZ");
var dateTime2 = DateTime.Parse("2024-05-15T04:20:05.069Z");
var dateTime3 = DateTime.Parse("2024-05-15T04:20:05.0690000Z");

Console.WriteLine($"dateTime1: {dateTime1.Ticks} - {dateTime1.Hour}:{dateTime1.Minute}:{dateTime1.Second}.{dateTime1.Millisecond}");
Console.WriteLine($"dateTime2: {dateTime2.Ticks} - {dateTime2.Hour}:{dateTime2.Minute}:{dateTime2.Second}.{dateTime2.Millisecond}");
Console.WriteLine($"dateTime3: {dateTime3.Ticks} - {dateTime3.Hour}:{dateTime3.Minute}:{dateTime3.Second}.{dateTime3.Millisecond}");
Console.WriteLine($"dateTimeString: {dateTimeString}");

Output:

dateTime1: 638513436050690000 - 4:20:5.69
dateTime2: 638513436050000069 - 4:20:5.0
dateTime3: 638513436050690000 - 4:20:5.69
dateTimeString: 2024-05-15T04:20:05.069Z

Aditional information

I looked at the code a bit and I don't have a good solution at the moment.

[networkfusion]

My common workaround is .ToString("o")

e.g. you can use Debug.WriteLine($"as ISO date: {DateTime.FromUnixTimeSeconds(shadow.timestamp).ToString("o")}");

[CoryCharlton]

My common workaround is .ToString("o")

e.g. you can use Debug.WriteLine($"as ISO date: {DateTime.FromUnixTimeSeconds(shadow.timestamp).ToString("o")}");

My issue is that the strings I need to parse are coming from an API I don't have control over.

My current workaround is some IndexOf/Substring hacking to find the fractional seconds part and pad/trim it to 7 digits.