feat: improve date handling in birth number generation

Author: p333ter

README.md

@@ -6,7 +6,7 @@
 [![Coverage Status](https://img.shields.io/coveralls/github/p333ter/birth-number-utils?style=flat-square)](https://coveralls.io/github/p333ter/birth-number-utils)
 [![Build Status](https://img.shields.io/github/actions/workflow/status/p333ter/birth-number-utils/publish.yml?style=flat-square)](https://github.com/p333ter/birth-number-utils/actions)
 
-A TypeScript/JavaScript library for generating, validating, and parsing Czech and Slovak birth numbers (rodné číslo).
+A TypeScript/JavaScript library for generating, validating, and parsing 🇨🇿Czech and 🇸🇰Slovak birth numbers (rodné číslo). Built for reliability, performance, and ease of use.
 
 ## Installation
 
@@ -25,12 +25,29 @@ import { generateBirthNumber } from '@ppasmik/birth-number-utils';
 const randomBirthNumber = generateBirthNumber();
 console.log('Random Birth Number:', randomBirthNumber); // e.g., "900720/3117"
 
-// Generate a birth number with specific parameters
-const customBirthNumber = generateBirthNumber({
+// Generate using string date (recommended)
+const birthNumber1 = generateBirthNumber({
+  gender: 'MALE',
+  birthDate: '1985-11-19', // November 19, 1985 (YYYY-MM-DD format)
+});
+
+// Generate using Date object (note: months are 0-based in JavaScript Date)
+const birthNumber2 = generateBirthNumber({
   gender: 'FEMALE',
-  birthDate: new Date(1990, 6, 20), // 20th July 1990
+  birthDate: new Date(1990, 6, 20), // July 20, 1990 (month 6 = July)
 });
-console.log('Custom Birth Number:', customBirthNumber); // e.g., "905720/3111"
+```
+
+⚠️ **Important Note About Dates**:
+
+- When using string dates (recommended): Months are 1-based (1 = January, 12 = December)
+- When using JavaScript Date object: Months are 0-based (0 = January, 11 = December)
+- Examples:
+
+```typescript
+// These create the same birth number (November 19, 1985):
+generateBirthNumber({ birthDate: '1985-11-19' }); // string format
+generateBirthNumber({ birthDate: new Date(1985, 10, 19) }); // Date object (10 = November)
 ```
 
 ### Validate Birth Numbers

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "@ppasmik/birth-number-utils",
-  "version": "2.0.6",
+  "version": "2.0.7",
   "description": "A TypeScript/JavaScript library for generating, validating, and parsing Czech and Slovak birth numbers (rodné číslo).",
   "author": "Peter Pasmik",
   "license": "MIT",

package.json

@@ -100,6 +100,24 @@ describe('Birth Number Validation and Parsing', () => {
       }
     });
 
+    it('parses valid male birth number', () => {
+      const birthDate = new Date(Date.UTC(1985, 10, 19));
+      const birthDate2 = generateBirthNumber({
+        birthDate: "1985-11-19",
+        gender: "MALE"
+      });
+      const result = parseBirthNumber(birthDate2);
+
+      expect(result).not.toBe(false);
+      if (result) {
+        expect(result.birthDate).toEqual(birthDate);
+        expect(result.gender).toBe('MALE');
+        expect(result.isMale).toBe(true);
+        expect(result.isFemale).toBe(false);
+        expect(result.birthDateAsString).toBe('19.11.1985');
+      }
+    });
+
     /**
      * @description Parses valid female birth number and verifies all details.
      */
@@ -122,7 +140,7 @@ describe('Birth Number Validation and Parsing', () => {
      */
     it('correctly calculates age and validates dates', () => {
       const result = parseBirthNumber('0001018336');
-      expect(result).not.toBe(false);
+      expect(result).not.toBe(true);
       if (result) {
         const currentYear = new Date().getFullYear();
         const expectedAge =

src/__tests__/birthNumber.test.ts

@@ -1,8 +1,13 @@
 import dayjs from 'dayjs';
+import customParseFormat from 'dayjs/plugin/customParseFormat';
+import utc from 'dayjs/plugin/utc';
+
+dayjs.extend(utc);
+dayjs.extend(customParseFormat);
 
 export interface BirthNumberOptions {
   gender?: 'MALE' | 'FEMALE';
-  birthDate?: Date;
+  birthDate?: Date | string;
 }
 
 export const generateBirthNumber = (
@@ -12,15 +17,15 @@ export const generateBirthNumber = (
     ? dayjs(options.birthDate)
     : dayjs().subtract(Math.floor(Math.random() * 72 + 18), 'years');
 
-  let month = birthDayjs.month() + 1;
+    const year = birthDayjs.format('YY');
+    const day = birthDayjs.format('DD');
+    let month = birthDayjs.month() + 1;
+
   if (options.gender === 'FEMALE') {
     month += 50;
   }
 
-  const firstPart =
-    birthDayjs.format('YY') +
-    month.toString().padStart(2, '0') +
-    birthDayjs.format('DD');
+  const firstPart = year + month.toString().padStart(2, '0') + day;
 
   let controlPart = Math.floor(Math.random() * 10000)
     .toString()
@@ -39,4 +44,8 @@ export const generateBirthNumber = (
 
 // Pre zachovanie spätnej kompatibility môžeme exportovať alias funkcie:
 export const generateCzechBirthNumber = generateBirthNumber;
+
+
+
+
 export const generateSlovakBirthNumber = generateBirthNumber;

src/generators/generateBirthNumber.ts

@@ -1,3 +1,7 @@
 export { BirthNumber, rodnecislo } from './classes/BirthNumber';
-export { generateBirthNumber } from './generators';
+export {
+    generateBirthNumber,
+    generateCzechBirthNumber,
+    generateSlovakBirthNumber
+} from './generators';
 export { isValidBirthNumber, parseBirthNumber } from './validators';