No. 13, body of the letter in the Princeton/Vilnius documents
Addressee: Barras; place: Passeriano; date: 4 Vendémiaire, An V[I] (25 September, 1797). In fact, Brotonne gives "an V" but the 4 Vendémiaire, An V is the 25th September, 1796. Since we have the autograph for this document (i.e., the Princeton/Vilnius documents and the facsimile in Coston) in which the year is missing, we know that the year is a conjecture. Now, since Bonaparte was not in Passeriano in 1796, the correct date must be 1797, so the error in the dating in Brotonne is not for the Gregorian but rather the Republican calendar - "an V" should read "an VI".
Brotonne published only part of the text of this letter (up to "santé"). It is possible that Brotonne took the addressee here, Barras, from Coston, Biographie (1840), which he cites (here, note 1).