All the sources I've read say that Leonhard Euler presented his paper on the Konigsberg bridge problem to the St. Petersburg Academy on August 26, 1735.
However, they don't seem to agree on what year the paper was first published in journal form.
For example, Wikipedia gives 1741 as the year of the journal publication.
Euler's work was presented to the St. Petersburg Academy on August 26, 1735, and published as Solutio problematis ad geometriam situs pertinentis (The solution of a problem relating to the geometry of position) in the journal Commentarii academiae scientiarum Petropolitanae in 1741.
But page 3 of Norman L. Biggs, E. Keith Lloyd, and Robin J. Wilson's Graph Theory 1736--1936 (Oxford: Clarendon Press, 1998) states that the paper (L. Euler's Solutio problematis ad geometriam situs pertinentis in Commentarii Academiae Scientiarum Imperialis Petropolitanae, 8, 128-140) was published in 1736.
Was Euler's paper in volume 8, pages 128-140 of the Proceedings of the St. Petersburg Academy published in 1736 or in 1741?