You also get one on your 60th wedding anniversary.

I organised one for my grandparents a couple of years back. They also received a card from the Prime Minister [of New Zealand], the Leader of the Opposition, their local MP, and a couple of other random politicians and dignitaries.

It's not something that I thought about at the time, but I'm quite happy that it's something you need to apply for. It would be a bit disconcerting if the Queen had access to the birth, death, and marriage records of everybody in New Zealand.

Are birth, death and marriage records not public?

I don’t know about New Zealand, but nowadays in Australia recent births deaths and marriages records are only available to their subjects and close relatives. Two reasons (a) privacy (b) helps prevent identity theft, since birth certificates (and sometimes also marriage certificates) are often accepted as identity documents

Yes but localized and rarely digitized

For people in the states, you can get appropriate cards from the White House for important occasions.

I sent Bill Clinton an invitation to my high school graduation party, and got a letter back from the White House telling me to work hard in college.

But mailing a birth announcement to the White House is a much better idea. They send a card back to the child welcoming them to the world. You can file it away and then give it to your kid when they are an adult and tell them this is the first letter they ever got.

In Germany, the first letter a child gets is one that gets sent automatically, assigning them a tax number. A letter from the President is much nicer. However, German parents can apply for the President to be the honorary godfather of their seventh child.

The funniest thing with this tax letter is that on the envelope it says “Karriere mit Zukunft” meaning “careers with a future” like they completely seriously expect your newborn baby to start working for them 18+ years down the line.