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Old 19 November 2012, 01:30 PM
Troberg Troberg is offline
Join Date: 04 November 2005
Location: Borlänge, Sweden
Posts: 11,580

Originally Posted by Floater View Post
This happens every now and then and the reason is that the Swedish equivalent to social security numbers do not contain information about which century a person was born, only the two last figures in the year.
Actually, that's wrong, it does contain that information, but most people (and most computer systems) do not know it.

The format is yymmdd-nnnx if you are younger than 100, where:

yy: Year with two digits.
mm: Month, two digits.
dd: day, two digits. If it's a temporary number, for example a foreign national, 60 is added to this part.
nnn: Just a pseudorandom number, where the third digit is odd for men and even for women (this last bit has recieved a fair bit of criticism, as it's viewed as too narrow in it's definition of gender, as well as unnecessary information for the state to have). The first two digits used to show where you where born, but that has been abandoned and now it's just a pseudorandom number.
x: check number, based on the Luhn-algorithm (aka IBM MOD-10). It's the same algorith as the one used on credit cards.

On the day you turn 100, the format changes to yymmdd+nnnx, ie the dash becomes a plus.

However, as I said, it's a very common misconception that you can't see if a person is 100 or older.

Other common mistakes are using the wrong formats, such as yymmddnnnx, yyyymmddnnnx or yyyymmdd-nnnx. Even my bank does that mistake, but it's still wrong.

Worth noting is that organization numbers (which are assign to companies and other taxable organizational entities) uses the same format, except that the month part is always at least 20, the first digit shows the type of organization and rest of the date part is just pseudorandom numbers.
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