📋 Shiur Overview
Summary of Chapter 8 — Laws of Sanctification of the Month (Rambam)
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Law 1 — The Lunar Month: Twenty-nine Days, a Half, and Parts
Language of the Rambam: The lunar month is twenty-nine days, a half, and parts, as we have explained.
Plain meaning: The Rambam repeats the foundation from Chapter 6, that a lunar month is 29½ days plus parts (29 days, 12 hours, 793 parts). Chapter 8 begins with the calculation of how one carries out the months in practice — that is, the calculation of full and deficient months. (Chapters 6-7 were the “calculation called excellent for the matter of mitzvah”; Chapter 8 continues with the true calculation of establishing the lunar months.)
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Law 2 — It Is Impossible to Calculate Hours for Months
Language of the Rambam: And it is impossible to say that Rosh Chodesh should be part of the day from the previous month and part from the coming one… “until a month of days” — according to the tradition they learned that you calculate days for the month and you do not calculate hours. Therefore, they make the lunar months, some of them deficient months of only twenty-nine days, and some of them full months of thirty days, in order not to calculate by hours but by complete days.
Plain meaning: One cannot make Rosh Chodesh begin in the middle of the day. The source is the verse “until a month of days” (Numbers 11:20), from which the Sages learn that a month consists of days — complete days — not hours. Therefore, sometimes one makes a deficient month (29 days) and sometimes a full month (30 days).
Insights and explanations:
1. The Rambam’s source — the Rabbis of Caesarea (Megillah 5a): The Rambam brings the exposition from “until a month of days” as a practical law for establishing the months. The Gemara in Megillah 5b says: “The Rabbis of Caesarea in the name of Rabbi Abahu, from where do we know that we do not calculate hours for months? As it says ‘until a month of days.’” The Rambam learns this as a law in establishing the months itself — that essentially the molad can occur in the middle of the day (according to the calculation of the molad which is halacha l’Moshe miSinai), but one may not make Rosh Chodesh in the middle of the day.
2. The Yad Peshutah (Rabbi Rabinowitz) explains that the Rambam’s interpretation only fits according to his position that the calculation of the molad is halacha l’Moshe miSinai. With the calculation of the molad, the molad can indeed occur in the middle of the day (for example, four in the afternoon), and therefore one needs an exposition that one only counts complete days. But with sanctification of the month based on sighting, the question is less relevant, because the sighting of the moon is in any case at night.
3. Rashi’s interpretation — a Choshen Mishpat / monetary matter: Rashi learns the Gemara differently — not as a law in establishing the months, but as a law in monetary matters/vows: when someone says “I lend you money for a month” or makes a condition for a month, one goes by days not by hours. The Rambam does not follow Rashi’s interpretation. Rashi’s interpretation also makes sense, but the Rambam’s interpretation fits better with the context of “the Rabbis of Caesarea” who were engaged in establishing the months.
4. Another exposition in that Gemara — “there are no days of years for years”: In that Gemara there is also an exposition regarding years — that one should not make the year according to days (i.e., instead of intercalating a month every third year, one should not add a few days every year). It is not clarified how the Rambam learns that exposition, but he speaks of it later.
5. [Digression: In practice with sanctification based on sighting — when did Rosh Chodesh become?] When the Beit Din sanctified the month based on sighting, Rosh Chodesh only became from the moment that the Beit Din sanctified (not from the beginning of the day). “The day is reckoned from when the rabbis say” — i.e., Rosh Chodesh begins when the Beit Din rules. It is asked whether one had to say Ya’aleh v’Yavo out of doubt from the beginning of the day, and it is noted that “the commentators struggle” with this in practice. What is certain is that the Mussaf offering was brought after the Beit Din sanctified.
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Law 3 — Parts Beyond the Half Day
Language of the Rambam: However, the parts that are in each and every month beyond the half day, there will accumulate from them hours and days, until some years will have deficient months more than the full ones, and some years will have full months more than the deficient ones.
Plain meaning: If a month were exactly 29½ days, one could simply make 6 deficient and 6 full months every year. But because there are additional parts beyond the half day (the month is 29 days, 12 hours, 793 parts), hours and days accumulate, and therefore sometimes there are more deficient months than full ones, and sometimes the reverse. The calculation of how this works — when full and when deficient — is the essence of Chapter 8.
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Law 4 — The Thirtieth Day, Two Days of Rosh Chodesh, and the Order of the Months
Part A: The Thirtieth Day and Two Days of Rosh Chodesh
Language of the Rambam: The thirtieth day is always added as Rosh Chodesh in this calculation. If the previous month was deficient, the thirtieth day will be Rosh Chodesh of the coming month. And if the previous month was full, the thirtieth day will be counted as part of it as Rosh Chodesh, and it will be the completion of the full previous month, and the thirty-first day will be Rosh Chodesh of the coming month.
Plain meaning: The thirtieth day is always counted as Rosh Chodesh in this calculation. If the previous month was deficient (29 days), the thirtieth day is already Rosh Chodesh (one day of Rosh Chodesh). If the previous month was full (30 days), the thirtieth day is still part of the old month, and Rosh Chodesh is only the thirty-first day — therefore there are two days of Rosh Chodesh.
Insights and explanations:
1. “Counted as part of it as Rosh Chodesh” — what does “part of it” mean? The Rambam’s language “part of it” is explained as follows: because the month is 29½ days (approximately), when the previous month is full (30 days), the old month essentially ended in the middle of the thirtieth day — the first half of the thirtieth day still belongs to the old month, and the second half should already be Rosh Chodesh. But because one cannot divide a day (according to the law of “you calculate days”), one counts the entire thirtieth day still for the old month (completion of the full previous month), and the thirty-first day becomes Rosh Chodesh. This is the foundation of two days of Rosh Chodesh.
2. The Rambam’s unique reason for two days of Rosh Chodesh: The Rambam gives a unique reason for why the first day of Rosh Chodesh (the thirtieth day) is called “Rosh Chodesh” — because “part of it is Rosh Chodesh,” the calculation of the new month begins in the middle of that day. That is, the second half of the day is already the new month, but because one cannot make a “part of the day” — one makes the entire day Rosh Chodesh, even though it is halachically the thirtieth day of the old month. This is an innovation of the Rambam — not a doubt about the day (like the “normal” answer for why one has two days of Rosh Chodesh, similar to when they would sanctify based on sighting when one did not know if witnesses would come), but rather a reasoning based on “part of the day.”
3. Question on the Rambam’s reason: The reason of “part of it is Rosh Chodesh” only fits when the previous month was full — then one indeed took 30 days for a month that is really only 29½, and therefore part of the thirtieth day is already the new month. But when the previous month was deficient (29 days), 29 days later is still not even the molad — then why should the first day of Rosh Chodesh be called Rosh Chodesh? The reason thus depends on what the previous month was, and this requires investigation.
4. Another question on this approach: If one makes the month full (30 days), one has already taken a half day from Rosh Chodesh and said that it is not Rosh Chodesh — i.e., one has delayed Rosh Chodesh by half a day. This is the price of the principle that one only counts complete days.
Part B: The Order of Full and Deficient Months
Language of the Rambam: The order of full and deficient months according to this calculation: Tishrei full, Tevet deficient, from Tevet onward one full and one deficient in order — Tevet deficient, Shevat full, Adar deficient, Nisan full… And in a leap year — first Adar full and second Adar deficient.
Plain meaning: The Rambam lays out the order of months: Tishrei full, then he jumps to Tevet deficient, and from Tevet onward it goes one full one deficient. Cheshvan and Kislev are skipped because they are not fixed.
Insights and explanations:
1. Cheshvan and Kislev — the variable months: All months are fixed (full or deficient), except Cheshvan and Kislev. This is why the Rambam jumps from Tishrei directly to Tevet.
2. Three states of Cheshvan/Kislev:
– Shanah sheleimah (complete year) — both full
– Shanah chaserah (deficient year) — both deficient
– K’sidran (in order) — Cheshvan deficient, Kislev full (this is the “normal” order: Tishrei full, Cheshvan deficient, Kislev full, Tevet deficient…)
3. Cheshvan full and Kislev deficient does not occur — this is never a possibility in the calendar.
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Law 5 (or Continuation of Law 4) — How to Determine if a Year is Complete, Deficient, or In Order
Language of the Rambam: One counts the number of days between Rosh Hashanah of this year until Rosh Hashanah of the coming year. For a regular year: 2 days = deficient, 3 days = in order, 4 days = complete. For a leap year: 4 days = deficient, 5 days = in order, 6 days = complete.
Plain meaning: One looks at which day of the week is Rosh Hashanah of this year, and which day of the week is Rosh Hashanah of the coming year, and one counts how many days in between (not including both Rosh Hashanahs themselves). According to the number of days, one determines whether the year is deficient, in order, or complete.
Insights and explanations:
1. The logic of this calculation: The calculation shows us how many days are in the year in total. If one has more days than the minimum, one needs to “fill in” with extra days — that is, Cheshvan and/or Kislev become full. With 2 days (regular year) is the minimum — both deficient. With 3 days — in order (one full, one deficient). With 4 days — both full.
2. Leap year: Because a leap year has another month (30 days), one adds another 2 days to the calculation (because 30 modulo 7 = 2). Therefore: 4 days = deficient, 5 = in order, 6 = complete.
3. The Rambam’s example: Rosh Hashanah is Thursday (fifth day), next Rosh Hashanah is Shabbat — this is 3 days in between — in order. If next Rosh Hashanah is Tuesday (third day) — 4 days — complete. If Rosh Hashanah is Shabbat and next is Tuesday — 2 days — deficient.
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Signs to Confirm the Calculation
Language of the Rambam: They have signs — there are signs (rules) that one can use to check the calculation of establishing the year.
Plain meaning: After one has calculated the calculation from Rosh Hashanah to Rosh Hashanah, one can use three signs as a “check” to confirm that the calculation is correct. The signs are not an independent calculation, but rather a confirmation mechanism.
Insights and explanations:
1. Sign 1 — Tuesday (third day): If Rosh Hashanah falls on Tuesday, then the months are in order — whether in a regular year or in a leap year. One does not need to calculate whether it is complete or deficient — it must be in order. But whether it is regular or leap one still needs to know from the previous calculation.
2. Sign 2 — Sunday or Monday (first day or second day): If Rosh Hashanah falls on Sunday or Monday, it is never in order — it must be either complete or deficient, but which of the two one still needs to calculate.
3. Sign 3 — Thursday (fifth day): If Rosh Hashanah falls on Thursday, it depends: in a regular year it cannot be deficient (two deficient is ruled out). In a leap year it cannot be in order.
4. Practical use: After one calculates the calculation of how many days from Rosh Hashanah to Rosh Hashanah, one should check all three signs — and this gives a verification that the calculation is correct. The specific calculation of why each sign is correct can be found in the commentators.
5. Conclusion: With this one has almost all the tools that one needs to make a calendar — the calculation of the molad, the postponements, the establishment of deficient/in order/complete, and the signs to confirm.
📝 Full Transcript
Chapter 8 — Establishing the Lunar Months: Full and Deficient Months
Law 1 — The Lunar Month: Twenty-nine Days and a Half and Parts
Speaker 1: And in Chapter 8 he will explain to us what he’s talking about. Right? Okay. He says like this:
The lunar month, a month of the moon, comes out to twenty-nine days and a half and parts, as we have explained.
That’s what he clarified earlier.
Speaker 2: Where are you? Chapter 8? Chapter 6?
Speaker 1: Yes. What is Chapter 6? We’re in Chapter 8, yes yes. We’re in Chapter 8. So he begins…
Speaker 2: What? The solar year?
Speaker 1: Ah, sorry, sorry, sorry, I’m in the wrong place. I need to go back to the lunar month. Very good.
Now we’re going to learn what the true calculation is, supposedly, right? That’s the idea? Chapters 6 and 7 we learned the calculation called… it’s over there.
Speaker 2: Do it backwards.
Speaker 1: That’s not your mic today. If you want, you can take down the other piece. I put the mic because I was told it’s better. I don’t know. Let’s find out.
Chapters 6 and 7 were the calculation called excellent for the matter of mitzvah. Now they’re going to find out something else, I don’t know. Let’s see. Establishing the lunar months. Let’s see. He says, the lunar month, the month of the moon, we discussed earlier, is twenty-nine days and a half and parts. This is Chapter 8, right? Come to the first section, Chapter 8. Okay.
Law 2 — It’s Impossible to Calculate Hours for Months
Speaker 1: So he says, it’s twenty-nine days and a half and parts. Supposedly it should often come out that Rosh Chodesh should be in the middle of the next day, because it’s twenty-nine and a half. But it’s impossible to say that Rosh Chodesh should be part of the day from the previous month and part from the coming one, that one day should be divided in half. I mean, what would be? If we were autistic, four in the afternoon, new month. It doesn’t become a month. What would be so bad?
Speaker 2: A verse.
Speaker 1: No, I understand why you don’t need a verse for this. It’s not practical, but one could seriously perhaps accept it, just like Shabbos becomes a certain time.
Speaker 2: No, today Shabbos becomes a certain time because we are modern people who don’t live with the sun. Normal people, Shabbos becomes the opposite, Shabbos becomes a whole day. Actually that it doesn’t become, is something that needs examination. I mean, it needs examination perhaps on us, but…
Speaker 1: In short, there’s a verse on this. I would have said such a reasoning. It says in the verse “until a month of days”. According to the tradition they learned, they learned from this verse that there’s a decree… “until a month of days” is a term in a Gemara. Interesting, according to the tradition they learned. “That you calculate days for a month and you don’t calculate hours”. So from this verse one learns that days are, so to speak, a month. That is, a month consists of days. A month doesn’t consist of hours. No, a month has nothing to do with hours. A month consists of days. The hours are in the small calculations. Hours, go there to the small children, there they talk about hours. We are the bigger numbers. Okay.
“Therefore we make the lunar months, some of them deficient months”, one must do, instead of every time a half would have been good. But instead of making every time a half, one must sometimes add a day and sometimes subtract a day. “Some of them deficient months, twenty-nine days only”. A deficient month we make 29 days, even though it’s still missing 12 hours with strong parts. “And some of them full months, thirty days”, even though there’s simply an extra hour. “In order not to calculate by hours but by complete days”, so that it should always come out that we calculate by days. Interesting.
Discussion: The Rambam’s Interpretation of the Gemara — Comparison with Rashi
Speaker 1: This is the Rambam’s interpretation of the Gemara, “From where do we know that we don’t calculate hours for months”. I remember that Rashi… The verse was speaking in a time when it was still according to sighting, and according to sighting it did often go by hours, that Rosh Chodesh was in the middle of the day.
Speaker 2: No, no, no. I only knew that Rosh Chodesh was in the middle of the day. Rosh Chodesh was a whole day.
Speaker 1: What the Rambam certainly learned, you were too late. Hillel the Second already said, he did a good thing. We already spoke that the laws are complicated. The point is, but if it wasn’t too late for Rosh Chodesh…
Speaker 2: The day is calculated from the evening.
Speaker 1: I can be that a doubt would arise that one should already say Yaaleh Veyavo out of doubt from the beginning of the day.
Speaker 2: Again, that’s the question. The commentators struggle with how one conducted oneself in practice, something is not clear. This is certain that the sacrifice was brought afterwards, a sacrifice can be brought until the afternoon Tamid. But you’re right.
Speaker 1: So let’s see, let’s see very well. So this is a Gemara, it says in Megillah 5a, “The Rabbis of Caesarea in the name of Rabbi Abahu, from where do we know that we don’t calculate hours for months? As it says ‘until a month of days’”. This is the source of the Rambam. So he’s actually explaining that this only works with the… this only works with the… Very good. He says, you see, Rav Yad Peshutah, Rav Rabinowitz, explains that the calculation only goes with the Rambam’s approach, that the calculation of the molad is a law given to Moses at Sinai. And in the calculation of the molad it can come out four in the afternoon the molad. It can’t come out the sighting, it can only be at night. Anyway, one doesn’t see the moon in the middle of the day, it’s not a question.
Speaker 2: Now, Rashi in general learns differently. Rashi learns that the midrash is not a midrash about how one makes a month. It’s a legal matter. One says a month, how long is a month? One cannot say, that is, a scholarly matter, that it’s more a Choshen Mishpat matter, or a get, some condition. Someone says, “I will lend you money for a month”, does it mean according to hours or does it mean according to days? The Gemara says, it goes according to days.
Speaker 1: Why doesn’t he agree with Rashi? I mean not why not, I mean that Rashi’s sense makes a lot of sense.
Speaker 2: The Rambam says, yes, the Gemara here look, “there are days for years, as it says”. I don’t know what this comes in here at all.
Speaker 1: One must know, the Rabbis of Caesarea were those who were engaged in establishing the months. One must know where the Rabbis of Caesarea came from. Rashi’s interpretation makes sense if the Rabbis of Caesarea were a Jewish court. They’re only bringing a source for something that’s simple.
Speaker 2: The Rambam says, this is a law regarding the Torah scholars who are engaged in establishing the months.
Speaker 1: No, not really. Regarding the way the law should work with months. It’s essentially other words, it’s only a source for something that’s essentially simple. It’s clear that even when the Gemara says, one doesn’t calculate. Yes, it’s a whole day. It doesn’t go like that. It’s only three times a spark. I don’t know, I don’t know, I’m already convinced that Rashi’s interpretation is a bad interpretation.
Speaker 2: What’s the other interpretation? It’s in the second year. What does that mean?
Speaker 1: Also, that one shouldn’t make the year.
Speaker 2: Yes, as you said, that instead of making every third year over the year, one should make every year a few days.
Speaker 1: I won’t go the plan, I won’t go plan, I didn’t have another plan, I didn’t have any luck. Rashi says it further, that which someone made a vow, he won’t be deaf for a whole year. Does it go according to the months, not according to the years, not according to days.
Speaker 2: And how does the Gemara learn in that Gemara? Does it say a day for years?
Speaker 1: I don’t know, he doesn’t say so later he goes about this. In short, one can understand that it’s not clear matters, it’s simple that a month is a day. Okay, let’s continue.
Speaker 2: Yes?
Speaker 1: No. Yes, just a moment. Since we cannot make any half days a Rosh Chodesh, we make twenty-nine and thirty. Right?
Law 3 — Parts in Addition to the Half Day
Speaker 1: Section 3 you say, yes? “These are months that are not clearly twenty-nine days and months that are not clearly thirty days”. Let’s see what’s coming, I still know. Okay, when it would have been exactly, right? It would have been twenty-nine days, ah, and a half, and a half. If it would have been twenty-nine days and a half, ah, twenty-nine and a half, one would have made simply every month, six deficient months, six full months. “However the parts that are in each and every month, in addition to the half day, will accumulate from them hours and days, until some years will have deficient months more than full ones, and some years will have full months more than deficient ones.”
Speaker 2: One must figure out if it comes out every year a whole extra day?
Speaker 1: No, it doesn’t come out every year, less than every year. Therefore, sometimes one must do this way, sometimes that way. He doesn’t say why. On this they didn’t make the calculation, how does this come out?
Speaker 2: Yes yes, it’s also the calculation. Let’s see honestly. Yes yes, because then, still a part of the calculation. And we’re going to learn the calculation.
Speaker 1: In short, now learn the calculation, let’s say, Chapter 8 is the calculation of full and deficient months. We haven’t learned yet how we do this. When does one make full, and when does one make deficient?
Law 4 — The Thirtieth Day and Two Days of Rosh Chodesh
Speaker 1: So it is, “The thirtieth day we always add it as Rosh Chodesh in this calculation. If the previous month was deficient, the thirtieth day will be Rosh Chodesh of the coming month. And if the previous month was full, the thirtieth day will rise, part of it as Rosh Chodesh.” Ah, part of it rises as Rosh Chodesh. Interesting. Therefore, “And it will be the completion of the full previous month, and the thirty-first day will be Rosh Chodesh of the coming month.” Because if the previous month was full, it’s simple that it continues into the thirtieth day is still the previous month.
Speaker 2: Part of it?
Speaker 1: The relevance of part of it. What does part of it mean? One makes two days of Rosh Chodesh.
Speaker 2: Rebbe Meir asks, what makes two days of Rosh Chodesh?
Speaker 1: He says, because since the previous month was a full month, so it comes out that essentially the month ended deep into the thirtieth day, yes, half the day. It ended half a day into the thirtieth day.
Speaker 2: I don’t know, it turns like one holds, I don’t hold exactly. Right, then when it’s twenty-nine and a half… still a… explain to me clearer.
Discussion: Why Two Days of Rosh Chodesh?
Speaker 1: The thirtieth day, normally, the thirtieth day is 29 and a half, so after half a day is Rosh Chodesh. That’s the simple meaning. But… The calculation that a month is 29 plus a half, it’s simple that the last day and another half of it, and yesterday was 29, and today the first half is the 29 half. So essentially you still belong to the previous month. But the second half should already have been Rosh Chodesh. Very good.
Speaker 2: Now, why does this have to do with the previous month being full?
Speaker 1: Carry out. I made actually a month of thirty days. It comes out now that what? As one makes that Rosh Chodesh is only the thirty-first.
Speaker 2: Yes. It’s the opposite, I took half a day from Rosh Chodesh and said that it’s not Rosh Chodesh.
Continuation of Law 4 – Reason for Two Days of Rosh Chodesh
The Rambam’s Approach
Speaker 1: Sometimes one does this way, sometimes one does that way. But what does he say? “Since part of it is Rosh Chodesh, and the full previous month will be completed”. Therefore it’s still the 30th of the previous month. The day is actually Rosh Chodesh regarding the law.
What does “part of it is Rosh Chodesh” mean? Translate “part of it”. Half of this day is the new month. Half of this day is the new month, because the day is twenty-nine and a half. So the first half of it is still the previous month, the thirtieth day of the previous month, and the second half is the first day of the new month, yes?
He says that often there is a Rosh Chodesh that one still counts as the 30th day of the previous month, and the next day one counts the second day of Rosh Chodesh is the 1st day of the new month. That’s what he says here.
And he says here why one does so, because the first day of Rosh Chodesh must actually be Rosh Chodesh, because it already begins, the calculation already begins in the middle of that day, but only in the middle of that day, because essentially the previous month is 29 and a half. So one counts it as the 30th day of the previous month. One gives it a name Rosh Chodesh, because in the middle of the day the new month comes in. So one says Hallel, whatever, one gives it a name Rosh Chodesh, but it’s the 30th day of the previous month.
Question on the Rambam’s Reason
Speaker 1: I’m not crazy, I’m not the first one who’s adding something here. As the people here are also missing.
What’s the meaning of why this is Rosh Chodesh? It doesn’t make sense. It’s exactly the opposite, if the previous month was full, then twenty-nine days later isn’t even the new moon at all yet.
Supposedly, one wants to say a reason why the first day of Rosh Chodesh is called Rosh Chodesh, okay? This was said if it was the previous month. If we make a full month, and then we make the next day Rosh Chodesh, I understand. Approximately every second, I understand, very good. Because why do you call the first day Rosh Chodesh? There’s a normal answer, because there wasn’t once a doubt.
Yes, according to sighting, because there wasn’t according to sighting, one always made such a doubt. Ah, there’s a doubt of the day that remained. Like a doubt of the day. That’s the normal answer.
The Rambam puts some new answer, that part of the day is because part of the day is Rosh Chodesh. I don’t know what that means. Based on the previous idea, that the whole reason we have this is because one can’t make any part of the day, but here one does calculate with part of the day.
I don’t understand. I’m not the only one who doesn’t understand, because it actually turns on what the previous month was. So in short, it needs examination. Okay.
In short, let’s go further.
Law 3 – The Order of Full and Deficient Months
The Establishment of the Months
Speaker 1: They ask the question, that it doesn’t fit, it doesn’t come, never is the great order. This is a normal commentator on the page, on my page. Okay, therefore one makes this calculation. This is simple, it would have worked out.
Normally one goes in calculation one day Rosh Chodesh, second month two days Rosh Chodesh, right? Very good.
Ha, “The order of full and deficient months according to this calculation, Tishrei full, Teves deficient, Teves and onward one full and one deficient in order, Teves deficient, Shevat full, Adar deficient, Nissan full.”
Let’s learn this calculation. Right? And in a leap year both months one makes deficient. No, first Adar full and second Adar deficient. Okay, these are the months that are fixed.
Cheshvan and Kislev – The Variable Months
Speaker 1: But the two months, Cheshvan and Kislev, because we skipped, we said Tishrei full, Teves deficient. But what about Cheshvan and Kislev?
These two months have all kinds of ways how they can be. Right? It can be both full, it can be both deficient, and it can be Cheshvan deficient and Kislev full.
Speaker 2: It can be the opposite?
Speaker 1: No. Right? But what’s never there, Cheshvan full and Kislev deficient?
Speaker 2: I don’t know so.
The Names of the Years
Speaker 1: Now, there’s an interesting name, the years have names. If both are full it’s called… all the holidays are in full months, Nissan, Sivan and Tishrei. Okay.
The reason however is simple, one made every second. The only months that are different are Cheshvan and Kislev, which can be all kinds of things.
If both are full it’s called a complete year. If both are deficient it’s called a deficient year. If it’s called Cheshvan deficient and Kislev full it’s called in order, because that’s the normal order, Tishrei full, Cheshvan deficient, Kislev full. So ah, about this it goes on this order. Very good. One goes back to the normal one-one order.
Law 4 – How One Determines if a Year is Complete, Deficient, or In Order
The Calculation According to Rosh Hashanah
Speaker 1: Now, how does one know? You want to know the calculation? How does one know which year is the year to make?
Speaker 2: What does it mean which year is the year?
Speaker 1: First you must know which day is Rosh Hashanah. They learned Chapter 7, right? They explained that Rosh Hashanah is lo adu, because in any case one of the other four days of the week it can be, according to the calculation of what was learned in Chapter 7, make a calculation of the last year, all the molads and things, right? You’ll know when Rosh Hashanah is.
“Calculate the number of days between them”. Except for the leap day, is the day between what and what?
Speaker 2: I don’t know.
Speaker 1: When days between? It’s the two years, right? As if from this Rosh Hashanah until the previous Rosh Hashanah, right? Until next Rosh Hashanah, sorry.
Speaker 2: No, make a calculation from Rosh Hashanah to Rosh Hashanah as the year, from Rosh Hashanah 5785 to Rosh Hashanah 5786.
Speaker 1: If there are two days, meaning from Monday to Wednesday, yes? Then it’s chaserim (deficient). If you’ll find three days, it’s kesidran (regular). If you’ll find four days, it’s shleimim (full).
Discussion: How Does the Calculation Work?
Speaker 2: How does one calculate this? I don’t know.
Speaker 1: No, that means… I mean, why does this show that it’s shleimim? That all the months are shleimim?
Speaker 2: Or uh, the two months?
Speaker 1: What is the question?
Speaker 2: Yes, Cheshvan and Kislev. Everything here is talking about Cheshvan and Kislev.
Speaker 1: From the words of the Amoraim, let’s take out the chapter from the words of the Amoraim, that this is a shanah peshutah (regular year), then the calculation works.
Apparently the calculation simply shows us how many days there are in the year altogether, if it needs to be filled in with, understand? If there are four days, simply I have more… right?
Speaker 2: Yes, from the outside you can see, if there are four days, you have another two days that you need to add to the year. How do they find the two days? Add it like this. If it’s three days, it’s correct.
Speaker 1: Yes, that’s the calculation. However, this only works for a shanah peshutah, because then it’s only four days. If it’s me’uberet (leap year), then you need to have five days, right? So if there are four days, it’s chaserim. If it’s five days, it’s kesidran. If it’s six days, it’s shleimim. Very simple. Right? Because in a shanah me’uberet there are indeed two more months.
Speaker 2: No, one more month.
Speaker 1: That means, one needs to add another day to the calculation.
Examples from the Rambam
Speaker 1: Keitzad (How so)? After the Rambam illustrates. Keitzad? Rosh Hashanah shel shanah zo peshutah hayah beyom chamishi, v’Rosh Hashanah shel shanah haba’ah hayah beyom Shabbat, harei yesh beineihem gimmel yamim (How so? Rosh Hashanah of this regular year was on Thursday, and Rosh Hashanah of the coming year was on Shabbat, behold there are three days between them).
Yes, from Thursday to Sunday is three days. One knows that the year is in the calculation of chaser, Kislev malei (full) like the normal.
If Rosh Hashanah is afterwards on Tuesday, and it comes out how many days do we have in between? From Thursday to Tuesday is how many days do we have?
Speaker 2: How much is it?
Speaker 1: It’s four days. Then it’s shleimah (full).
If the Rosh Hashanah is Shabbat and the next year is Tuesday, it comes out there are only two days in between.
Signs to Confirm the Calculation of Kevi’at Hashanah
The Signs that the Rambam Brings
Simple. There are other signs. Let’s see what the signs are. It makes it easier to check that one hasn’t made a mistake.
Yesh lahem simanim, simanim shetuyim aleihen (They have signs, foolish signs upon them), because it says here in the calculation of the order of the year, and there is no building on the foundation of this calculation and the establishment and the beginning of its ways. They built everything on this calculation.
And therefore, every year, it should be so, every year that Rosh Hashanah is Tuesday is kesidran. Did you know? Because why does one need to figure out the calculation why does it come out? If Rosh Hashanah is Tuesday, it must be that whether peshutah or me’uberet, what is it? That the months are kesidran.
If it’s Sunday or Monday, it’s never kesidran. That means, but which it is, we don’t yet know. This you’ll still need to use the previous calculation. That means, whether it’s malei or chaser, two full and two deficient.
If it’s Thursday, it depends. If it’s peshutah, then it can’t be chaserim. If it’s me’uberet, it can’t be… uh, it can’t be kesidran. Sorry.
Very good. If Rosh Hashanah is Thursday, you know that for us, Rosh Hashanah peshutah, you know that it can’t be chaserim. And if it’s me’uberet, you know that it can’t be kesidran.
The Role of the Signs
These are signs, certain rules that one can use to check whether the calculation is correct, what you’ve done is correct. Yes, that’s what it means.
It says here, he means to say after you’ve done the calculation of how many days it is from Rosh Hashanah to Rosh Hashanah, you should check the three signs, one, two, three signs, then you’ll have a check on your calculation, correct. You’ll have a check, you’ll know whether your calculation was correct or not. This is a simple check.
And the check has indeed worked itself out from a calculation that I want to figure out. What is it? Presumably you’ll look in the commentaries and say what the calculation is. Make a chart, or something.
Now you already know almost how to make a calendar, right? Okay.
Conclusion
Good, that’s the story. The people want to sleep a little.