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internal static DateTime GetFirstMonday(int month, int year)
{
    var dt = new DateTime(year, month, 1, 12, 00, 00);
    for (var i = 0; i < 7; i++)
    {
        if (dt.DayOfWeek == DayOfWeek.Monday)
        {
            return dt;
        }

        dt = dt.AddDays(1);
    }
    
    Console.WriteLine($"Unable to find 1st monday for year '{year}' and month '{month}'!");
    return DateTime.MinValue;
}