You're contradicting yourself, how can it be unique if only 1000 can be assigned per given date of birth? What if more than one thousand babies are born in the country one day?
replyIt's Denmark, it won't have 1k babies born the same day.
replyIt's the same in Sweden: YYYY-MM-DD-XXXX is the format for a personnummer, double the population of Denmark and there are no collisions.
There have been collisions in Sweden, but that was due to lots of immigrants coming from the middle east that did not know when they where born. So many of them picked first of January. They “solved” it by overflowing to the next days.
replyCompletely forgot about the YYYY-01-01 case!
replyThanks for correcting it :)
Immigrants who don't know their birthdate are assigned xxxx-01-01, so they have actually run out of numbers for January 1st in some years.
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replyThat format looks like it would allow for up to 10k per day. Unless one of those X's is a check digit?
replyThey said sex is encoded in it, so it’s probably a sex digit.
replyedit: I was wrong. Wikipedia says, “The first digit of the sequence number encodes the century of birth (so that centenarians are distinguished from infants)”.
It also says “the last digit of the sequence number is odd for males and even for females”. What a strange system. Essentially the last three digits are two different sequences made to look like one.
That's a problem for future Denmark!
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