One of the hazards of being someone who is at least moderately a data nerd is the fact that questions tend to become opportunities for research. Recently I was chatting with one of our congregation’s deacons as well as with our associate pastor and the subject of the timing of the Passover on days of the week came up. The deacon could only think of three days of the week in which the Passover came up and I thought it would be worthwhile to check out his suppositions by the data. The immediately relevant point was that the Feast of Weeks can only come on a certain day of the week (namely the first) and therefore there is only a limited range within the Hebrew calendar that the Pentecost can be celebrated on based on the day of the week where the Passover falls, since, as both Leviticus 23 and Joshua 5 tell us, the wave sheaf offering that begins the count takes place on the morrow after the weekly Sabbath that must also be the morrow after the Passover, where it is possible to eat unleavened bread and offer up the wave sheaf on the same day.
Therefore, I thought to calculate, based on the date that Passover took place (knowing that Passover begins on the evening before the date), the evenings in which the Passover can occur when one follows the rules of postponement set out by Hillel II. To be sure, there are a variety of ways for the calendar to be figured out when one departs from these rules of postponement. One can look for visible crescents rather than the calculated calendar. One can set rules that would keep Abib from coming before the vernal equinox, or even follow the sidereal year, as I have heard others do. It is not my purpose to discuss the rules of postponement in detail, as they can be easily found elsewhere. What is my point is to discuss the impact these rules have on the days of the week where the Passover can occur. Since I was only able to easily obtain the Holy Day calendar for 2013 to 2026, this is a preliminary investigation. If anyone is able to locate and send me the information (via photograph or .pdf or something of that nature) for the historical dates going back before 2013 as early as possible, I will extend this investigation and look at the frequency of different days of the week to see if there are any which occur more often than others.
As it is, from 2013 to 2026, there are four nights of the week in which a Passover can occur. In 2013, 2014, 2017, and 2024, the Passover occurred on the first night of the week. In 2020, 2023, and 2026, the Passover is scheduled to come on the third night of the week. In 2015, 2016, 2018, 2019, and 2022 the Passover is scheduled on the fifth night of the week. And finally, in 2021 and 2025 the Passover is schedule to occur on the sixth night of the week. These are the only four nights in which the Passover occurs during this entire time. Each of them has, of course, different implications for when the Feast of Week occurs on a calendar date, as each night of the week leads to a different calendar date on which the Pentecost can occur. As it happens, each night of the week where the Passover can occur leads to a different date on the Hebrew calendar when the Feast of Weeks/Shavuot/Pentecost occurs. To wit, in 2013, 2014, 2017, and 2024 Pentecost comes on 10 Sivan. In 2020, 2023, and 2026, Pentecost comes on 8 Sivan. In 2015, 2016, 2018, 2019, and 2022, Pentecost comes on 6 Sivan. Finally, in 2021 and 2025 Pentecost comes on 5 Sivan, the earliest it can apparently occur, because it occurs when the wave sheaf and First Day of Unleavened Bread coincide (the Joshua 5 test case).
Having seen which days of the week the Passover can fall and the days of Sivan that Pentecost can occur based on the rules of postponement also provides the days they cannot occur. The Passover will never be on the second, fourth, or seventh night of the week. As a result of this, Pentecost will never fall on 7, 9, or 11 Sivan. Of course, it cannot happen on any other days of that month because of the requirement of seven sabbaths between the wave sheaf and the Pentecost, but it is noteworthy the effects that the rules of postponement have on the calculation of Passover as well as Pentecost. While the 14 years from 2013 to 2026 is a small sample size, it does demonstrate the broad range across the weekly, Hebrew, and Gregorian calendars that Holy Days can occur in sufficient to understand what options are permitted and what are forbidden. Of course, having more data points would allow for a determination of relative frequency distributions. So, if anyone has historical data for the Holy Day Calendar, please send it my way, as early as you have it.