Twenty-one years ago today, on May 5, 2004, there is no widely noted single event in the provided search results specifically tied to this exact date. However, looking at the broader context of the year 2004 and the early 2000s, several significant events occurred around that time, such as the ongoing global conflicts, political changes, and technological advancements noted in the timeline of the 21st century

. If you are interested in notable historical events that happened on May 5 in other years, for example, in 1980 the British SAS ended the Iranian Embassy siege in London, a significant counter-terrorism operation

. For a precise event exactly 21 years ago today (May 5, 2004), more specific historical records or news archives would be needed, as the search results do not pinpoint a major event on this exact date.