interesting calendar phenomenon
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December 13, 2021 8:27 pm at 8:27 pm #2041296ParticipantParticipant
this year pesach will be on shabbos
next year thursday
year after that tuesday
year after that sunday.all this can change if we revert to being mekadeish al pi eidem.
December 13, 2021 10:46 pm at 10:46 pm #2041336Reb EliezerParticipantSo Pesach will tell us all other holidays, see SA O’CH 428,3 by using reverse aleph beis א’ת, ב’ש, ג’ד, ד’ק, ה’צ, ו’פ and פל’ג.
December 13, 2021 10:47 pm at 10:47 pm #2041343Reb EliezerParticipantPesach reveals all other holidays, see SA O’CH 428,3.
אדו לא ראש Rosh Hashana cannot fall on Sunday because then Hashana Rabba would fall on shahbbos and knocking down the hoshanas would be eliminated. It cannot fall on Wednesday or Friday as we cannot have to consecutive days were no work can be done. So Yom Kippur cannot fall on Friday or Sunday respectively and as a consequence בדו לא פסח.December 13, 2021 10:48 pm at 10:48 pm #2041385☕️coffee addictParticipantIyH b’karov (seems like pieces are falling into place)
December 14, 2021 12:03 pm at 12:03 pm #2041592Yabia OmerParticipant“this year pesach will be on shabbos
next year thursday
year after that tuesday
year after that sunday.”I don’t get it. What’s the interesting phenomenon?
December 14, 2021 1:25 pm at 1:25 pm #2041620GoldilocksParticipantYabia Omer, the interesting phenomenon is this: There are 4 possible days of the week that the first day of Pesach can fall out on. 2022 – 2025 will be a four year span where we have Pesach occurring on each of the four possible days.
It’s interesting to note that we had the same phenomenon during the years 2021 – 2024.
After 2025, the first day of Pesach won’t occur on Sunday again for approximately 20 years.December 14, 2021 2:20 pm at 2:20 pm #2041664Reb EliezerParticipantAs indicated before:
If Pesach is on shabbos, so Rosh Hashana will be Monday so is Sukkos, the first and last days.
Yom Kippur on Wednesday and Shavuos Tuesday.
When Pesach is on Thursday, Rosh Hashana will be Shabbos, so is Sukkos.
Yom Kippur is Monday and Shavuos on Friday,
When Pesach is on Tuesday, Rosh Hashana will be Thursday and so is Sukkos,
Yom Kippur is Shabbos and Shavuos Wednesday,
When Pesach is on Sunday, Rosh Hashana is Tuesday and so is Sukkos.
Yom Kippur is Thursday and Shavuios on Monday.December 14, 2021 3:30 pm at 3:30 pm #2041689GoldilocksParticipantReb Eliezer, that’s almost right.
When the first day of Pesach is on Shabbos, Shavuos will begin on a Sunday, not on a Tuesday.December 14, 2021 5:09 pm at 5:09 pm #2041751Reb EliezerParticipantThe Purim before Pesach is the sixth day of Pesach and Purim and Lag Baomer fall the same day.
December 14, 2021 5:10 pm at 5:10 pm #2041749Reb EliezerParticipantGoldilocks, thank you for your correction. Shavuos is the day after Pesach (ב’ש) and not after Rosh Hashana.
December 15, 2021 7:58 am at 7:58 am #2041912GoldilocksParticipantAnother interesting calendar phenomenon:
This past Rosh Hashana occured on Tuesday and Wednesday.
Next year Rosh Hashana will occur on Monday and Tuesday.
However, next year Chanuka will occur on the exact same days of the week as this year, with Rosh Chodesh on Shabbos and Sunday, just as this year.
Go chew on that one. 😃🍩December 15, 2021 7:58 am at 7:58 am #2041908GoldilocksParticipantDuring a nonleap year, Asara B’Teves will fall on the same day of the week as Purim.
During a leap year, Asara B’Teves will fall on the same day as the following Simchas Torah.December 15, 2021 7:59 am at 7:59 am #2041887BuggyParticipantThis wasn’t interesting at all.
December 15, 2021 9:43 am at 9:43 am #2041930Reb EliezerParticipantThe climate changes through the seasons determined by the sun whereas Jewish holidays are determined through the moon. Pesach is spring and Sukkos fall time causes a Jewish leap year 7 times in 19 years in order that lunar year having normally 354 days and the solar year 365 1/4 days even itself out. The mnemonic is guchadzut, 3, 6, 8, 11, 14, 17, 19 year in 19 years becomes a Jewish leap year. A calendar is available in the Tur after siman 428 which enumerates each of the 19 years determined by Cheshvan and Kislev if they are deficient, both 29 days, full, both 30 days or even one 29 days and the other 30 days. The rest of the months cycle between 29 and 30 days. 6×29 + 6×30 = 174 + 180 = 354 days. The variation of the two months above causes the movement of Rosh Hashanah as Adu lo Rosh, the Rosh Hashanah cannot fall on Wednesday or Friday. Rosh Hashanah cannot be on a Sunday in order Hashanah Rabba should not fall on a shabbos eliminating the knocking off the hashanas and Yom Kippur should not be next to shabbos in order that there should not be two consecutive days where work is not allowed.
December 15, 2021 9:44 am at 9:44 am #2041923GadolhadorahParticipant“….This wasn’t interesting at all. ..”
Definitely not unless you earn your parnassah providing consulting services on when/how to make an eruv tavshilim or a travel agent worrying about tradeoffs between midweek travel discounts and when its “safe” to book a flight for your frum clients worried about being stranded erev yom tov.December 15, 2021 11:51 am at 11:51 am #2041976ubiquitinParticipantRE
“The variation of the two months above causes the movement of Rosh Hashanah as Adu lo Rosh”
Phrasing is backwards, Lo Adu Rosh (along with the other dechuyos) causes the variation of the two months.
December 15, 2021 1:34 pm at 1:34 pm #2041998GoldilocksParticipantAs Reb Eliezer pointed out, we have a 19 – year cycle of leap years and non – leap years.
We are currently in year 6.December 15, 2021 1:34 pm at 1:34 pm #2042001Reb EliezerParticipantubi, you are right.
December 15, 2021 1:51 pm at 1:51 pm #2042010Reb EliezerParticipantThere is one more dechiya, pushing Rosh Hashana to the next day, if the molad of Tishri would be in the afternoon of the day that Rosh Hashana would have been designated. By any other Rosh Chodash we would make two days Rosh Chodash and count the next month from the second day but by Rosh Hashana we count Tishri from the first day.
December 15, 2021 6:04 pm at 6:04 pm #2042144ParticipantParticipant“There are 4 possible days of the week that the first day of Pesach can fall out on. 2022 – 2025 will be a four year span where we have Pesach occurring on each of the four possible days.
It’s interesting to note that we had the same phenomenon during the years 2021 – 2024.”
It’s in reverse order of the days of the week in 578285 which IMO is more interesting. i can’t speak for buggy or GH, of course.December 15, 2021 9:37 pm at 9:37 pm #2042166GoldilocksParticipantIf the molad of Tishrei occurs on Monday or Tuesday morning, under certain circumstances Rosh Hashana may be pushed off to the next day, due to reasons very few people understand (and I’m not one of them:) ).
December 16, 2021 10:53 am at 10:53 am #2042350ubiquitinParticipantGoldilocks
Today you are!
It is all spelled out in Rambam Kidddush Hachodesh 7 wit hmefarshim there as well as end of hilchos Rosh chodesh in OC
first Tuesday it is more common and a bit easier
The time between one molad and the next is 29 days 12 hours and 793 chalakim ( a chelek is 1/1080 of an hour which equal 3 and 1/3 seconds)
Since 28 days is 4 full weeks One month’s molad will occur 1 day 12 hours and 793 chalakim later in the week.
A regular year is of course 12 months, if you multiple 1 day 12 hours 793 by chalakim and remove full weeks)
You end up wit h4 days 8 hours 876 chalakimThus for example the molad Of Tishrei 5781 Was Thursday 20 hours 701 chalakim
If you add 4 days 8 hours 876 Chalaikm
you get molad tishrei 5782 which was Tuesday 5 hours 497 chalakimRosh Hashana 5781 was pushed off to Shabbos, since Molad occured after 18 hours (noon) and cant be Friday becasue Lo Adu Rosh
Rosh Hashana of this year 5782 was not pushed off and was on Tuesday, the day of the moladHowever if the molad occurs on a tuesday after 9 hrs 204 chalakim (G”T”RD gimmel is 3 for tues tes 9 for 9 hours 204 chalakim) Then Rosh Hashana That year would be Tuesday
The next molad occurs 4 days 8 hours 876 Chalaikm later in the week Whci his Shabbos, 18 hours 0 chalaikm. This is molad Zaken pushed to Sunday then Pushed to Monday Because of the first 2 dechuyos)
A Year that begins on Tuesday and whose final day is Sunday is 356 days long this is too long (options are 354 if all months alternate 29/30, 353 if bot h chesvan Kislev have 29 and 355 if both have 30)
So we push off Rosh Hashana from Tuesday thursdayThe monday Dechiya is rarer still, in fact it will not occur again until after 6000
The idea is the same except it comesu p after leap yearsthe difference between molad Tishrei before a leap year and after is 13 x (112793) = 5 days 21 hrs 589 Chalakim
As mentioned Molad tishrei 5782 was Tuesday 5 hours 497 chalakim
NExt Year’s molad tishrei 5782 will be Monday 3 hrs 6 chalakimHowever if Molad of year after leap year is on Monday 15 hrs 589 chalakim or later
The previous years’ molad was 5 days 21 hrs 589 Chalakim earlier whci his Tuesday 18 hours.That Rosh hashana gets pushed off because molad zaken then lo adu Rosh to Thursday. If we keep the year after leap year on Monday the year is 382 days long this is too short options for leap year are 383 384 385 (regular year + 30) so we push off the year after leap year to tuesday
hope this helps
December 16, 2021 1:18 pm at 1:18 pm #2042388Reb EliezerParticipantMentioned in Sefer Shevil Harakia we find one of the most interesting gematrios:
החדש הזה לכם ראש חדשים ראשון הוא לכם לחדשי השנה adds up to 2658 the same as כמה תשעה ועשרים יום ומחצה ותשצג חלקים
how much 12 1/2 days and 793 chalokim (from one molad to another) where a chelek is 1/1080.
1080 is divisible by 2,3,4,5,6,8,9,10,12.15,16,18,20,24,30,32,36December 16, 2021 2:04 pm at 2:04 pm #2042421Reb EliezerParticipantThat is an 1/1080 of an hour.
December 16, 2021 6:40 pm at 6:40 pm #2042526Reb EliezerParticipant1080 is not divisible by 16 and 32.
December 18, 2021 6:39 pm at 6:39 pm #2042892ParticipantParticipantwhy is it that pesach never lands on Sunday twice consecutively?
Why can’t Chanukah start on Tuesday? IT should be possible when Rosh Hashana is Tuesday, 1 Cheshvan Thursday, 1 Kisleiv Shabbos. 1 Teiveis Monday, 1 Shvat Tuesday, 1 Adar Wed 1 Nisan Thursday.
December 18, 2021 6:57 pm at 6:57 pm #2042898ParticipantParticipantI just messed up those dates.
On a reg year Pesach would be Friday, on a leap year Sunday.
I had a way it worked out, but i can’t remember how.December 18, 2021 8:56 pm at 8:56 pm #2042918ubiquitinParticipantanswer to question 2 had some mistakes this is correct:
2) “Why can’t Chanukah start on Tuesday?”
for Chanuka to start on Tuesday You would need Rosh Hashana on Tuesday and the year “shalem” meaning that cheshvan and Kislev both have 30 days* In such a year 1 Kislev would be Shabbos 22 Kislev would be 3 week late on Shabbos, 23 sunday, 24 Monday 25 Tuesday.
However such a year is impossible a shalem year has 355 days if regular and 385 days for leap year
For a regular year Rosh Hashana would occur 355 days later ie 50 weeks and 5 days, which means Rosh Hashana would be Sunday – an impossibility
For a leap year Rosh Hashana would occur 385 days later ie after exactly 55 weeks. That would mean Rosh Hashana on Tuesday, while this is THEORETICLY possible, in reality it isnt becasue 2 Tuesdays back to back are impossible see Question 1*It doesn’t matter how many days Kiselv has for this , but the choices are 29 for both Cheshvan and Kislev 29 for Cheshvan and 30 for Kislev or 30 for both. there is no possibility of 30 for Cheshvan and 29 for Kislev
December 18, 2021 8:56 pm at 8:56 pm #2042915ubiquitinParticipant1 “why is it that pesach never lands on Sunday twice consecutively?”
Pesach on Sunday is linked to Rosh Hashana on Tuesday.
In order for Rosh Hashan to fall on Tuesday the molad has to occur between noon on Monday and at the latest noon on Tuesday * The molad from one tishrei to the next is never that close together it is either 4 days 8 hours 876 Chalaikm later in the week in a regular year and 5 days 21 hrs 589 Chalakim in a leap year.* in most years ie regular years it has to occur in an even narrower window until 204 chalakim after 3 AM (six hours note: this is using mean solar time) as mentioned in my earlier comment in this thread
2) “Why can’t Chanukah start on Tuesday?”
for Chanuka to start on Tuesday You would need Rosh Hashana on Tuesday and the year “shalem” meaning that cheshvan and Kislev both have 30 days* In such a year 1 Kislev would be Shabbos 22 Kislev would be 3 week late on Shabbos, 23 sunday, 24 Monday 25 Tuesday.
However such a year is impossible a shalem year has 355 days if regular and 385 days for leap year
For a regular year Rosh hashana would occur 355 days later ie 50 weeks and 5 days, which means Rosh Hashan would be Friday – an impossibility
For a leap year Rosh Hashana would occur 385 days later ie after exactly 55 weeks. That would mena Rosh Hashana on Wednesday – again impossible*It doesnt matter how many days Kiselv has for this , but the choices are 29 for both chesvan and Kislev 29 for Chesvan and 30 for Kislev or 30 for both. there is no possibility of 30 for cheshvan and 29 for Kislev
December 19, 2021 4:52 pm at 4:52 pm #2043162ParticipantParticipantI messed up on my correction, too. Pesach can land on a Sunday, in which case Chanukkah on Tues should be possible in a leap year.
@ubiquitin answered that R”H can only be on Tues if the molad is after noon on Monday. why is that? The 1st available allowed day for R”H has to be R”H? In other words why can’t the molad be on Sunday and not have r”h til tues?December 19, 2021 7:13 pm at 7:13 pm #2043179ubiquitinParticipant“The 1st available allowed day for R”H has to be R”H? ”
Generally yes. Rosh Hashana is on the day of the molad Tishrei. I’m not a 100% sure wha t you are suggesting “why can’t the molad be on Sunday and not have r”h till tues?” Are you suggesting it just be arbitrary? why would Rosh Hashana be Tuesday if the molad was Sunday?
The Troah tells us “Hachodesh Hazeh Lachm” as the Gemara learns “Kezeh re’eh vekadesh” when the new moon is seen Beis din is mikadesh Rosh Chodesh. Today of course we (ie chazal) do it al pi cheshbon, but it still isnt arbitrary. The cheshbon is based on the molad * (either becasue a moment after that is the new mooon, although it is invisible for few hours, or because at some point on Earth the moon could be visible on Rosh Hashana which is sort of how the Baal Hamoar explains.
Regardless, the date of Rosh hashana is determined by the molad, al pi cheshbon. It is not arbitrary.
However as mentioned, and as outlined in Rambam Kiddush hachdesh perek 7. There are 4 dechiyos/postponements when Rosh Hashana is pushed off.
Most famously Lo adu Rosh
Second one is molad Zaken if molad is at noon or later R”H is pushed off (this can combine with the Lo adu Rosh for a 2 day push if Molad occurs after noon on Tuesday, R”H would be pushed to Wed, then Lo adu Rosh so pushed to Thursday.There are 2 other dechiyos that are more technical, and less common.
But none of these dechiyis are arbitrary. IF the molad is Sunday why would R”H be Tuesday?
“I messed up on my correction, too. Pesach can land on a Sunday, in which case Chanukkah on Tues should be possible in a leap year.”
Yes theoretically possible in a leap year, except to Rosh Hashanas on Tuesday in a row are impossible
* A good question is why this only applies to Rosh Hashana and not every month. which are somewhat arbitrary compared to the molad. I assume this is because the calendar would be way too complicated trying to adjust every month to coincide with the molad. As long As Rosh Hashana is accounted for , that enough.
.December 19, 2021 7:13 pm at 7:13 pm #2043186PekakParticipantChanukah never falls out on Monday night going into Tuesday. It’s the only time it can never fall out.
December 20, 2021 6:50 pm at 6:50 pm #2043565ParticipantParticipant@ubiquitin u answered the question yourself. Many times Rosh Chodesh happens a day or two after the molad. And, as u mentioned that Rosh Hashana isn’t “arbitrary,” “Why would it be pushed off for no reason” “It can be pushed off…..Lo Adu Rosh.” There we go. so it’s not arbitrary, but there are dechuyos–even something not because of R”H itself but because of the consequences of having R”H being on certain days….so why can’t it be pushed off for the simple reason of maintaining a 29 day month?
December 21, 2021 8:05 am at 8:05 am #2043664ubiquitinParticipantParticipant.
The Rambam at the end of Perek 7 of Kiddush Hachodesh writes that the reason for Lo Adu Rosh, is because the the calculated molad is an average and often the real molad falls later. The make up for this discrepency We keep one day and push off one day.
The Raavad argues and says the reason for Lo Adu Rosh is the morecoomnly given reason to avoid Y”K o sunday/Friday and hoshana Rabbah on shabbos. This is not mentioned by the Rambam.
R’ Chaim Kanievesky in his Shekel Hakodesh explains that the Rambam doesnt disagree that those are why Ad”u were the days chosen to push off. He is just explaining why it is pushed off at all. If the calculated molad was the real molad there would never be any dechuyos, since it is an average and is not accurate which requires occasional adjustments, we push off for these other reasons. Though still not arbitrary.
I don’t understand why maintaining a 29 day month is important? and what would be the driving factor to determine whether to keep 29 days or not? if every year was always 354 days alternating 29/30 It would quickly fall away from the molad ( the average molad is not 29.5 days it is 793 chalakim longer) and even from the seasons as the 19 year cycle wouldn’t fit either
December 23, 2021 7:36 pm at 7:36 pm #2044438ParticipantParticipantthanks

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