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Editorial Team
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Asked: 2026-06-14T08:49:13+00:00

I have a piece of code which parses and validates user input: DateTime myDateTime

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I have a piece of code which parses and validates user input:

DateTime myDateTime = DateTime.Parse(userInput,currentCulture);

Current culture is being set (to en-ca or fr-ca) and the user Input is always in ISO 8601 format “yyyy-MM-dd”.

If the user enters 1900-01-01 the date is created as expected. If the input is “1900-01+01” the date time created is 1899-12-31 6:00:00 PM No exception is thrown, the DateTime.Parse happily converts this to the wrong date.

To make this work I am using DateTime.ParseExact(userInput,"yyyy-MM-dd",currentCulture).

So my question is not how to make this work (I have that) but whats up with the +01 or any + value? Am I missing something in ISO standard?

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1 Answer

  1. Editorial Team

    The only + in ISO8601 is in time offset part, and it looks like it is parsed this way in this case. But as far as I know all 3 parts of date required to have valid value before time offset is allowed.

    I’d recommend using DateTime.ParseExact(userInput,"yyyy-MM-dd",... (maybe even with InvariantCulture).

    DateTime.Parse accepts huge variety of inputs and tries to make best guess on users intentions. This feels like a case when it simply guesses in confusing way.

    Sample values (first local PDT, 2 other with explicit time offset):

    DateTime.Parse("1900-02"   ).ToUniversalTime()    //  2/ 1/1900  8:00:00 AM 
DateTime.Parse("1900-02+00").ToUniversalTime()    //  2/ 1/1900 12:00:00 AM
DateTime.Parse("1900-02+03").ToUniversalTime()    //  1/31/1900  9:00:00 PM

    Which seem that Parse essentially treats "YYYY-MM+0x" as "YYYY-MM-01T00:00+0x".

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