Many countries do use checksum digits, but I just found that Denmark is an interesting case where they no longer (!) require or use checksums that were previous

Many countries do use checksum digits, but I just found that Denmark is an interesting case where they no longer (!) require or use checksums that were previously mandatory. The reason is supposedly an increasing number of immigrants with uncertain dates who're then registered as born on January 1, or the first day in a month. Now that's a funny case of having to abandon best practices.