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interesting-facts.md

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+# Interesing facts about European national identification number
+
+While developing the [personal-code-to-birthday](https://rematocorp.github.io/personal-code-to-birthday/) library, I discovered fascinating differences in how various countries design their personal ID codes. Here are some of the insights I gathered:
+
+1. **🇺🇦 Ukraine:** Personal codes include the first five digits, which represent the number of days since January 1, 1900. This encodes the individual’s birthdate.
+2. **🇪🇪 Estonia:** Previously, personal codes included a detail about the hospital where the person was born. This practice has since been discontinued.
+3. **🇩🇰 Denmark:** In 2007, Denmark stopped using a check digit in personal codes because they were running out of unique code combinations.
+4. **🇱🇻 Latvia:** Starting in 2017, Latvia’s new personal codes no longer include the birthdate, which was previously part of the code.
+5. **🇱🇹 Lithuania:** The first digit of the personal code indicates the century and gender (e.g., 3 for males born in the 1900s, 4 for females born in the 1900s).
+6. **🇸🇪 Sweden:** When individuals turn 100 years old, their personal code is updated. The separator between numbers changes from a “-” to a “+”.
+7. **🇳🇴 Norway:** By 2032, Norway plans to remove gender and century indicators from personal codes, making them more neutral and less identifiable.
+8. **🇫🇮 Finland:** Personal codes include can include letters for advanced checksum.
+9. **🇷🇴 Romania:** Romanian personal codes contain an indicator for the county where the individual was born.
+10. **🇵🇱 Poland:** Personal codes modify month digits to indicate the century, e.g., January 1900s: 01, January 2000s: 21.