At 7:35 a.m. on November 13, 1872, Claude Monet started what has since become known as Impressionism. At least, that’s what a team of scientists led by Donald Olson of Texas State University have determined to be the exact date when the artist’s Impression, Soleil Levant (Impression, Sunrise) was painted, according to the Independent. The fact that the Impression, Soleil Levant spawned the movement has been long accepted in art historical circles. But experts have disputed when exactly it was created.

This latest investigation was spurred by Marianne Mathieu, the deputy director of Paris’ Musée Marmottan Monet in which the painting currently hangs. Leading up to this latest exhibition of the work she told the paper that “We wanted to pay tribute to this very important painting. Much of the history and details about this iconic work were unknown. With these techniques we could uncover new information.” Olsen was a natural choice, having previously dated works by Vincent van Gogh and Edvard Munch, among others.

Rather than using carbon or radiometric dating, Olsen and his team used known environmental conditions at the Le Havre harbor, which the painting depicts to determine what exact minute it captures. Previously, the painting was dated to 1873, but another essay in the catalogue for the exhibition also questions that date, thus supporting Olson’s findings. Monet signed the work “’72” but a previous, authoritative catalogue dated it to 1873. “There are no documents to confirm the exact date,” Mathieu explained to the paper, “and we wanted to explore if there were other ways to date it precisely.”