bchavez/Bogus · error · ArgumentOutOfRangeException

PESEL for the year below 1800 is invalid.

Error message

PESEL for the year below 1800 is invalid.

What it means

ExtensionsForPoland.Pesel encodes the birth date with a month shift that only has defined buckets for years 1800-2299 (in 100-year steps). A year below 1800 throws ArgumentOutOfRangeException. This is a hard limit of the PESEL encoding scheme.

Source

Thrown at Source/Bogus/Extensions/Poland/ExtensionsForPoland.cs:42

      {
         return (string)value;
      }

      return new StringBuilder()
         .AppendPeselDateOfBirth(person.DateOfBirth)
         .Append(person.Random.Number(9))
         .Append(person.Random.Number(9))
         .Append(person.Random.Number(9))
         .AppendPeselGender(person)
         .AppendPeselChecksum()
         .ToString();
   }

   private static StringBuilder AppendPeselDateOfBirth(this StringBuilder builder, DateTime dateOfBirth)
   {
      int monthShift = dateOfBirth.Year switch
      {
         < 1800 => throw new ArgumentOutOfRangeException("PESEL for the year below 1800 is invalid."),
         < 1900 => 80,
         < 2000 => 0,
         < 2100 => 20,
         < 2200 => 40,
         < 2300 => 60,
         _ => throw new ArgumentOutOfRangeException("PESEL for year above 2300 is invalid."),
      };

      return builder
         .Append((dateOfBirth.Year % 100).ToString("00"))
         .Append((dateOfBirth.Month+monthShift).ToString("00"))
         .Append(dateOfBirth.Day.ToString("00"));
   }

   private static StringBuilder AppendPeselGender(this StringBuilder builder, Person person)
   {
      return builder
         .Append(person.Gender == Name.Gender.Male

View on GitHub (pinned to 6ece18c5c2)

Solutions

1. Ensure Person.DateOfBirth.Year is >= 1800 before calling Pesel.
2. Generate birth dates with f.Date.Between(new DateTime(1900,1,1), DateTime.Today).
3. Guard against default(DateTime) (year 1) being assigned to DateOfBirth.

Example fix

// before
person.DateOfBirth = new DateTime(1750, 1, 1);
var pesel = person.Pesel();

// after
person.DateOfBirth = f.Date.Between(new DateTime(1960,1,1), DateTime.Today);
var pesel = person.Pesel();

int year = person.DateOfBirth.Year;
if (year < 1800)
    throw new ArgumentOutOfRangeException(nameof(year), "PESEL requires year >= 1800.");
var pesel = person.Pesel();

static bool PeselYearOk(int y) => y >= 1800 && y < 2300;

When it happens

Trigger: Calling person.Pesel() on a Person whose DateOfBirth.Year is less than 1800.

Common situations: Historical test data with a pre-1800 birth date, or an accidental DateTime.MinValue / default(DateTime) DateOfBirth.

Related errors

• PESEL for year above 2300 is invalid.
• {nameof(year)} must be between 1858 and 2057.
• {nameof(year)} must be between 1854 and 2039.
• {nameof(p.DateOfBirth.Year)} must be between 1900 and 2099.
• Gender not handled.

AI-assisted analysis of bchavez/Bogus@6ece18c5c2 (2026-08-13). Data as JSON: /api/errors/39aeed612ceb4696. Report an issue: GitHub.