François Hollande, who was elected President of France on 6 May 2012, was today, 15 May 2012, sworn in as the republic's new president. In accordance with the Andorran Constitution Article 43 Hollande also succeeded today as Co-Prince of Andorra (the other Co-Prince is the Bishop of Urgell, succeeded in 2003).
I have therefore updated my website Longest reigns today in order to reflect the event in Andorra (and France!).
Queen Elizabeth II of the United Kingdom, b. 1926, who celebrates her diamond jubilee this year, is the second oldest monarch of the world today (King Abdullah of Saudi Arabia, b. 1923, tops that list), and is also in second place in the list of the longest reigns of today's monarchs. The ailing King of Thailand, Bhumibol, b. 1927, succeeded already in 1946.