In Swallows and Amazons (SA), the treaty of offence and defence signed by the Swallows and the Amazons is dated "August 1929." There are many instances in Swallowdale (SD) that refer to action from SA as happening the previous year, but the card left on the summit of Kanchenjunga is dated "11 August 1931." Which year, therefore, is correct for SA--1929 or 1930? Since the date on the summit is the only specific date between the two books, this must be the start of the discussion.