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

CoryCharlton commented 4 months ago

Library/API/IoT binding

nanoFramework.CoreLibrary

Visual Studio version

No response

.NET nanoFramework extension version

No response

Target name(s)

No response

Firmware version

No response

Device capabilities

No response

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

No response

Screenshots

No response

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 commented 4 months ago

My common workaround is .ToString("o")

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

CoryCharlton commented 4 months ago

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.

nanoframework / Home