DateTime.ParseExact - different outputs on Windows 10 and WinServer2012R2

Question

I found out that this line:

DateTime.ParseExact("Jan 30", "MMM yy", null, System.Globalization.DateTimeStyles.None)

creates the date:

2030-01-01

...on my Windows 10 machine, but on Windows Server 2012 R2 the output is:

1930-01-01

Does anybody know how to get Windows Server 2012 to parse the date as 2000 instead of 1900?

Answer 1

It's based on the culture's default calendar's TwoDigitYearMax property. If you change that property value, you'll get a different result:

using System;
using System.Globalization;

class Program
{
    static void Main(string[] args)
    {
        var culture = CultureInfo.CurrentCulture;
        
        // Clone returns a *mutable* copy.
        culture = (CultureInfo) culture.Clone();
        
        culture.DateTimeFormat.Calendar.TwoDigitYearMax = 2029;
        var result = DateTime.ParseExact("Jan 30", "MMM yy", culture, System.Globalization.DateTimeStyles.None);
        Console.WriteLine(result.Year); // 1930

        culture.DateTimeFormat.Calendar.TwoDigitYearMax = 2129;
        result = DateTime.ParseExact("Jan 30", "MMM yy", culture, System.Globalization.DateTimeStyles.None);
        Console.WriteLine(result.Year); // 2030
    }
}