Problems for a lunar-solar sabbath system

In the previous post I described a sabbath-keeping system which starts on every new moon then observes every seventh day until the next. The Bible never describe such a system, though it may hint at it with verses such as Isaiah 66:23 and Ezekiel 46:1. The Bible does, however, mention some things that suggest such a system was not in use by the Children of Israel in the days of Moses.

Manna collection schedule

Moses gave the Children of Israel specific instructions for collecting manna in Exodus 16:19–29, in which he instructed them to collect enough for a single day, but on the sixth day to collect a double portion, so they wouldn't have to collect manna on a day of rest. But in the lunar-solar sabbath system outlined above, there are sometimes two sabbaths in a row, specifically the last day of a 29-day month, followed the next day by the first sabbath of the next month:

The Bible never (to my knowledge) documents instructions for collecting three days' worth of manna in preparation for back-to-back days of rest.

Similarly, for months of 30 days, there's only one day between sabbaths, and I'm not aware of any instruction to collect a double portion of manna on the day after a sabbath in preparation for sabbath the next day.

The Feast of Weeks

Leviticus 23:15–16 specifies the Feast of Weeks should occur 50 days after a sabbath, on a day after a sabbath. On a week-based calendar, that works out as described:

But such a count doesn't work in a lunar-solar sabbath system. The short week between the end of one month and the start of the next means that the 50th is not a day after a sabbath, but is either a sabbath or the day before it:

It's also not possible for any 50-day span to contain only "seven full weeks". It always comes up short, due to the insertion of the extra (not-full) week, and it always contains eight sabbaths.

Possibly English translations of Leviticus 23:15–16 assume a seven-day cycle and the original language leaves room for a lunar-solar sabbath system, but I'm not scholar enough in the original language to know. If you do, please email me.

Feast sabbaths

Another challenge is that many of the feasts outlined in Leviticus specify one or more additional sabbaths to observe, days of rest in addition to the regular weekly(-ish) sabbaths:

1. 1st month, 15th day - start of Feast of Unleavened Bread (Leviticus 23:5–8)
2. 1st month, 21st day - end of Feast of Unleavened Bread (Leviticus 23:5–8)
3. 7th month, 1st day - Feast of Trumpets (Leviticus 23:23–25)
4. 7th month, 10th day - Day of Atonement (Leviticus 16:29—31, 23:27–32)
5. 7th month, 15th day - start of Feast of Tabernacles (Leviticus 23:34–43)
6. 7th month, 22nd day - end of Feast of Tabernacles (Leviticus 23:34–43)

On a week-based calendar, those dates can fall on any day of the week, just like modern holidays based on a particular day of a particular month (e.g. New Year's, the Fourth of July, Christmas). But on a lunar-solar calendar, a given date in a given month always occurs on the same day of the week. The feast sabbaths listed above fall like this:

As you can see, of the six feast sabbaths listed above, four occur on days that a lunar-solar system already considered to be sabbath. Those feast sabbaths would already have been days of rest. (Note that because the first of the month is always sabbath, the day of the week isn't affected by whether the month has 29 or 30 days.)

It's possible those feast sabbaths could have had added requirements, above and beyond the more frequent sabbath observance, such as sacred assemblies, but Moses seems to put the emphasis on the dates much more than the rituals, and under a lunar-solar sabbath system, the dates would already have been observed specially.

Jeremiah

One final consideration is what the prophet Jeremiah meant in Lamentations 2:6 when he said God had made the Jews forget her sabbaths. That could mean several slightly different things:

1. The Jews had forgotten to observe their festivals and sabbaths
2. The Jews had forgotten how to calculate when to observe their festivals and sabbaths
3. The Jews had forgotten some specific information needed to calculate when to observe their festivals and sabbaths

Proponents of an obscure lunar-solar sabbath system might argue that Jeremiah meant #2, that the proper method was forgotten. Others might argue #3, that observers have forgotten which day of the week is an even number of seven-day cycles since the sabbath of Moses's era. Based on the type of admonitions given by the major prophets, I would suppose Jeremiah meant #1, but again, I'm no scholar in the original language.

Also, did Jeremiah mean the Jews had forgotten sabbaths permanently, or only temporarily? Failed observances can be resumed, and a lunar-solar sabbath system can only be forgotten temporarily, but an interruption to a seven-day cycle can cause the proper day to be forgotten in a way that can't be recovered.

A lot hinges on Jeremiah's intent, so if you have insight, let me know.