What is platinum jubilee?

According to Wikipedia:

In Commonweath countries such as England, Canada, New Zealand and Australia, the platinum jubilee is celebrated when a person or event reaches 70.

In South Asia countries such as India and Pakistan the platinum event is celebrated at 75 years or weeks.

In the USA, the term is not used. Instead the term 'diamond jubilee' is used to mark an event that reaches the 75 mark.