There are those who attempt to harmonize John and the synoptics by supposing that they disagreed not about when the Last Supper occurred, but about whether the date of Passover was supposed to be calculated by following a solar calendar or a lunar one. Annie Jaubert presents this theory in her book, The Date of the Last Supper (Staten Island: Alba House, 1965). This view cannot be accepted, however. It is too difficult to conceive of Passover having been celebrated twice in the same place without any contemporary or even later writer referring to such an event. Surely it would have been remarkable if two Passovers were held in the same week! Moreover, while we do know of solar calendars from the Book of Jubilees and the Temple Scroll, we do not know how any of these calendars really worked. Jubilees’s calendar, for instance, explicitly prohibits any form of intercalation (the adding of extra days in a leap year). And without intercalation, by Jesus’ time, Jubilees’s 364-day solar calendar would be off not just by days, but by months. It is only by hypothesizing some manner of intercalation that we can even come up with the possibility that in Jesus’ time the two calendars were both functioning, but off by just a few days. Thus in the end, Jaubert’s book presents a good theory, but it remains just that, a theory. For more on these questions, see James C. VanderKam, Calendars in the Dead Sea Scrolls: Measuring Time (London: Routledge, 1998).