Why is "Mona Lisa" smiling? Because she just found out she's 10 years younger. Indeed, the world's most famous painting was completed a decade later than previously thought. The "Mona Lisa" has long been dated 1503-6, but those dates will now be formally altered to 1503-19, the Louvre has confirmed. The change, reported by The Art Newspaper, is the result of new research on the Prado's recently-discovered copy of the famous portrait and on Leonardo da Vinci's "Virgin and Child with St. Anne."

According to the new research, all three works — the "Mona Lisa," "Virgin and Child With St. Anne," and the "Mona Lisa" copy, done by a Leonardo pupil — could have been worked on as late as 1519, shortly before the artist's death in May of that year. The rapid-fire series of scholarly discoveries that led to the redating began surfacing in March, when the Art Newspaper reported the news that started it all: the Prado had discovered the earliest-known copy of the "Mona Lisa." Additional research on the copy revealed it was completed later than previously thought — a fact that affected the bona fide "Mona Lisa" as well, as the two were completed side by side. (The background landscape in both the copy and the original was found to be based on a drawing dated 1515-1520, later than the original dates for both versions of the "Mona Lisa.")

A new wall label for the "Mona Lisa" with the revised dates is forthcoming. (We can't imagine anyone at the Louvre ever expected to reprint that one.) The Art Newspaper reports that the Prado copy will likely be taken to the Lourve for a few hours so that a small group of specialists can study the two works side by side, while the museum is closed.