Today I went to an exhibition on Pliny the Elder at the University Library in Naples, on the occasion of his 2000th birthday. I discovered that the famous eruption of AD 79 is now thought to have taken place in October or November, not in August, as previously thought. The library's deputy director, who was the curator of the exhibition, told me that the more reliable manuscripts of Pliny the Younger's famous letter have a date in November rather than August. Below is a copy of the Younger Pliny's letter 6.16, published in a 1470 edition of the Elder's Naturalis Historia, the year before the Editio Princeps of the Younger Pliny's letters was published. Notice that the month is left out, and it just says "VIIII kal. hora fere septima". I don't know which manuscript was used for this edition.