Can anybody provide the chronology of this, royal and papal, Europe and elsewhere, in the last 20 years?

The ones I recall are three in the year 2013: Queen Beatrix of the Netherlands, Pope Benedict XVI, and King Albert II of the Belgians.

In 2014, King Juan Carlos of Spain stepped down in favor his heir the Prince of the Asturias, now King Felipe VI.

In 2019, Emperor Akihito of Japan also abdicated the throne in favor of his heir, previously known as Crown Prince Naruhito.

The latest abdication I know of occurred last year, when Queen Margrethe II of Denmark stepped down after a reign of 52 years (the longest in the nation's royal history).

Have there been any others? I know that preparations are underway in Luxembourg for the transfer of reigns from Grand Duke Henri to Hereditary Grand Duke Guillaume. But that's no surprise, since His Royal Highness is only continuing the practice which has become customary in his country: he is following two precedents, just as Princess Beatrix did in the Netherlands.