In his chronicle of the events of 5431 [1671], Jacob Najara writes: ‘On 30 Iyar, Rabbi Samuel Tirmiso arrived’ in Adrianople.

At first sight, ‘30 Iyar’ seems about as likely a date as 30 February or 31 April: the Jewish calendar is structured so that the month of Iyar always has twentynine days. One's natural inclination is to suppose that ‘30 Iyar’ is an error of some sort. There are several reasons, however, why this inclination should be resisted.

First, the letter lamed, used to indicate the numeral 30, is distinctive and not readily confused with any other letter. It is not easy to imagine any transcriptional error that would have produced this misreading—especially one so apparently implausible.

Second, Najara tells us shortly afterwards that Nathan of Gaza arrived in Adrianople on 19 Sivan, and came to pay his respects to Sabbatai the next day, ‘on the sabbath day, the twentieth of the month’. According to Eduard Mahler’s tables, 20 Sivan 5431 would have fallen on Friday, 29 May. But now assume for a moment that Najara was working with a calendar that gave Iyar thirty days, so that 10 May 1671 would not have been the first day of Sivan (as in the standard Jewish calendar) but the last day of Iyar. 1 Sivan would then be not Sunday, 10 May, but Monday, 11 May. 20 Sivan would be Saturday, 30 May—in conformity with Najara.

Third, in the same sentence in which Najara describes Tirmiso's arrival, he says: ‘on the fourteenth of that month [Sivan] Rabbi Samuel Tirmiso … took leave of Amirah and returned home’. By Mahler's tables, 14 Sivan would have been a sabbath—an odd day to begin a journey. On the assumption that Najara’s ‘Iyar’ had thirty days, 14 Sivan = Sunday, 24 May. It would make perfect sense for Tirmiso to have spent sabbath in Adrianople and set out the next morning.

Now, in this very same sentence, Najara tells us (according to the manuscript) that the rabbis of Sofia arrived on 20 Sivan. We have just seen that, on the hypothesis of a thirty-day Iyar, 20 Sivan will be a sabbath, 30May.