A silver birthday refers to a 25th birthday. An organization may mark its silver jubilee with various celebrations, events and workshops throughout the year.
Jubilee refers to a special anniversary. Major jubilees are celebrated as 25, 50, 60 and 70 or 75 years. Golden jubilee refers to 50 years, while diamond jubilee is for 60 years. Both 70 and 75 years are called a platinum jubilee.
There are other special wedding anniversaries in between the major anniversaries. Bronze refers to a couple's eighth wedding anniversary. A 30th-year wedding anniversary is celebrated as a pearl anniversary. Ruby refers to a couple's 40th wedding anniversary. Precious metals like silver are commonly used for hierarchies, which convey conventionally perceived relative merit or value.