PESEL

PESEL (Powszechny Elektroniczny System Ewidencji Ludności) is Poland’s universal 11-digit citizen identifier. It encodes the holder’s birth date, birth century, gender, and an ordinal serial number.

Usage

import { Numerik } from '@slashlab/numerik-js'

// Boolean
Numerik.pesel().isValid('92060512186')   // true

// Rich result
const result = Numerik.pesel().validate('92060512186')
result.isValid   // true

// Parse to value object
const pesel = Numerik.pesel().parse('92060512186')

// Null on failure instead of exception
const maybe = Numerik.pesel().tryParse('bad-input') // null

Value object API

parse() and tryParse() return a Pesel instance.

Core

Method	Return type	Description
getRaw()	string	The original input, untouched.
getNormalized()	string	Whitespace-stripped digits.
toString()	string	Alias for getNormalized().

Extracted data

Method	Return type	Description
getBirthDate()	Date	Birth date decoded from the PESEL. Returns a new Date object, decoupled from the original.
getGender()	Gender	Gender.Male or Gender.Female.
getOrdinalNumber()	number	The 4-digit ordinal serial (digits 7–10). The last digit also encodes gender: odd = male, even = female.
getCentury()	number	The birth century as a base year, e.g. 1900, 2000, 2100.

Utility

Method	Return type	Description
isMale()	boolean	true when gender is Gender.Male.
isFemale()	boolean	true when gender is Gender.Female.
getAge()	number	Full years elapsed from birth date to today.
isAdult()	boolean	true when getAge() >= 18.

Examples

import { Numerik, Gender } from '@slashlab/numerik-js'

const pesel = Numerik.pesel().parse('92060512186')

pesel.getRaw()           // '92060512186'
pesel.getNormalized()    // '92060512186'
pesel.getBirthDate()     // Date — 1992-06-05
pesel.getGender()        // Gender.Female
pesel.isFemale()         // true
pesel.getOrdinalNumber() // 1218 (digits 7–10)
pesel.getCentury()       // 1900
pesel.getAge()           // calculated from today
pesel.isAdult()          // true

Century encoding

The month digits in a PESEL encode both the real month and the birth century:

Stored month range	Real month	Birth century
01–12	01–12	1900–1999
21–32	01–12	2000–2099
41–52	01–12	2100–2199
61–72	01–12	2200–2299
81–92	01–12	1800–1899

Failure reasons

Reason	Value	When
InvalidLength	invalid_length	Input is not exactly 11 digits after normalisation.
InvalidCharacters	invalid_characters	Non-digit characters remain after stripping whitespace.
InvalidMonth	invalid_month	Month encoding does not match any known century range.
InvalidDate	invalid_date	The decoded date is not a real calendar date.
FutureDate	future_date	The decoded birth date is in the future (strict mode only).
InvalidChecksum	invalid_checksum	Checksum digit does not match the computed value.
AllSameDigit	all_same_digit	All 11 digits are identical (strict mode only).

Validation algorithm

Weights: 1, 3, 7, 9, 1, 3, 7, 9, 1, 3

1. Reject inputs longer than 32 characters. Strip whitespace. Assert exactly 11 digits.
2. Decode birth date using the century encoding table above. Assert the date is a real calendar date. In strict mode, also reject birth dates in the future.
3. Compute checksum: multiply each of the first 10 digits by its weight, sum the products, take mod 10, subtract from 10, take mod 10 again. The result must equal digit 11.
4. In strict mode, reject inputs where all 11 digits are identical.

See Algorithms for the full reference.