It's definitely known in the English world albeit unusual:) What with divorce and all. I would say it's common knowledge in the US.

so nennen es unsere amerikanischen Freunde, mit denen wir ihre Silberhochzeit gefeiert haben.

Schau mal hier.

whether 25th or silver, in any case not just "wedding" but "wedding anniversary".

@the kat: I'd have said "silver wedding" too, without "anniversary" (It should be clear that the people celebrating this are not marrying for the 25th time ;o)). LEO agrees with me there.
Siehe Wörterbuch: silberhochzeit
AE/BE again, or a case for wrong entry?

(If you use the number instead of "silver", "gold" or whatever, you have to add "anniversary", of course)

People in the UK sometimes say "silver wedding" without the "anniversary".

Dragon, aber dann doch golden, nicht gold, oder?

Im übrigen werden in meiner nicht eingeheirateten Famile aus GB auch noch Ruby Weddings gefeiert.

OK, the ussual excuse then - must be an AE/BE thing... *gg*

...and probably Austrian, too...:-)

@spinatwachtel: Ja, natürlich, sorry.

@Gabby:

we say 25th wedding anniversary

(twenty-fifth)

we also say 25th wedding anniversary in California.

sorry- natürlich muss es 25 th heißen - habe in der Eile das th vergessen

The UK celebrates silver weddings, and ruby ones (40 years), as milestones on the way to the golden wedding (50 years) and even the diamond wedding (60 years).

See http://www.photocakes.co.uk/wedding_anniversa... for an example of a list of alleged anniversary names, but anything before the silver wedding should be taken with a large pinch of salt.