Guest Post: Halachic Zmanim In Polar Regions On The Kosher Antarctica Cruise

The RCGS Resolute in Waterboat Point, Paradise Bay, Antarctica on 12/17/18. Photo Credit: Moishie Hersko
DDMS IconNever Miss Another Deal - Follow DansDeals on Facebook

Dan’s note: One of my duties on the Kosher Antarctica Cruise last month was calculating the daily zmanim and setting up our daily prayer schedule, our 10 Teves fast times, and most critically, our Shabbos schedule. As I noted previously, we needed to find a cruise that departed on a Monday and returned on a Thursday. We did find one cruise that met all of our parameters, but the timing of the cruise was not exactly ideal. It departed on the 8th day of Chanuka and it was over a fast day. The cruise was also over the Shabbos that immediately preceded the southern hemisphere’s summer solstice. That meant that we would run into additional halachic issues about Shabbos and prayer times as the latitude at which there would be no darkness is much farther north during the weeks in close proximity to the summer solstice. But if we wanted to go, this was our only tenable option.

I spent many hours working with Rabbi Shmuel Lesches, who serves as a Magid Shiur in the Yeshiva Gedola of Melbourne, Australia, and Rabbi of Melbourne’s Young Yeshivah, working through the extremely complex halachos (Jewish Law) regarding zmanim in Polar regions. This was made more difficult as I did not know exactly where the cruise might wind up, as that is highly weather (and as it turned out, fuel) dependent. We also did not expect the ship to have WiFi available, which would create additional challenges in calculating zmanim based on a fluid location, until we learned that a new satellite based WiFi system was added just before our cruise. His research was instrumental in making sure that my own Rabbi was comfortable that we had appropriate answers for what to do based on several potential scenarios. 

Rabbi Dovid Heber of the Star-K was also very generous with his time and Polar Zmanim knowledge.

I asked Rabbi Lesches to share some background with readers who expressed an interest in knowing some of the inside baseball of what went into this. He spent countless hours doing research into our potential issues and here is an article that he wrote for DansDeals Readers about what went into that research. It covers merely a fraction of the overall potential issues that we discussed, but it gives a great technical background into what some of the issues were.

Yes, I’m still planning on finishing the Antarctica trip report as well 😉 . If you would like to see more guest posts like this, let me know which topics you would enjoy reading about!


By Rabbi Shmuel Lesches

When DansDeals broke the news about a Once-In-A-Lifetime Kosher Cruise to Antarctica, it immediately grabbed my attention. No, not for even one moment did the thought dawn in my mind that I would journey to the most remote continent on Earth. I knew all too well that I would not be availing myself of the opportunity to daven on the final terrestrial frontier with a Minyan of Jews from a diverse range of backgrounds. I would have to be content with mere pictures of the icebergs and seals, and I would have to make do with the local penguins that frequent the southernmost reaches of the Australian landmass I currently call home. Such is life!

What seized my attention was something else entirely. One of the many fascinating areas of Halacha concerns the calculation of Zmanim in the North and South Poles, or more widely, in the Arctic and Antarctic Circles. I have a strong interest in this realm due to its enormous, albeit little-known, relevance to the recent proliferation of transpolar flights. It is a topic that I have written about in the past, and I am currently in the process of rewriting an updated and expanded version (stay tuned IY”H!)

So, as soon as I heard about the DansDeals Cruise to Antarctica, the alarm bells began ringing. How would the passengers calculate davening and Shabbos times during the Antarctic summer, where daylight continues for months? This phenomenon lasts for six months straight at the actual South Pole, and for increasingly shorter durations of months and weeks as one moves northward to the edge of the Antarctic Circle, an imaginary line that is located at 66.56°S Latitude. For example, at the 80th parallel, there are about 130 days of uninterrupted daylight, at the 70th parallel there are about 70 such days, and near the 66th parallel (the edge of the Antarctic Circle), there are only several 24-hour periods of uninterrupted daylight.

Reb Yaakov Emden first posed the problem in the eighteenth century, albeit with regards to the North Pole. The issue was debated by a number of Poskim of that era, but the matter then receded into the background, presumably because the issue was not of a practical nature to most people. It was revived only in recent times, when modern travel made such questions practical. The most celebrated example was when Colonel Ilan Ramon, the first Israeli astronaut, joined a crew of NASA astronauts aboard space shuttle Columbia, which circled Earth once every 90 minutes. This meant that the astronauts experienced a day-night cycle every 90 minutes, and a “week” of seven such cycles lasted a mere ten and a half hours from start to finish! Would Ilan need to keep Shabbos every half day? (Even so, the issue of Shabbos observance in orbit is a somewhat opposite reality than Shabbos observance in the polar regions; at the Poles, the shift between daylight and darkness takes much longer than 24 hours, whereas in orbit, it takes much shorter than 24 hours.)

With Columbia’s tragic disintegration upon re-entry into the atmosphere, Colonel Ramon is no longer with us. With his demise, the question of how Halachic day and night is calculated in atypical situations again receded into the background. It is ironic that, specifically now, when transpolar traffic is growing at a rapid pace, the Halachic status of Polar day and night is paid scant attention, and not much advice of a practical nature is readily available to the frequent flyer. By the same token, many of the fundamentals were potentially relevant to the DansDeals Cruise. In fact, some of the issues would need to be explored even more deeply.

Halachic Day & Night in the Arctic Circle

So, how exactly are Zmanim calculated in places where daylight or darkness lasts longer than 24 hours? In the interests of keeping this article as concise as possible, we will list the multitude of opinions briefly, noting that there are four general approaches:

  1. Halachic day and night does not exist at all, and any Mitzvos that rely on Halachic time are not observable in the North Pole. [Kol Yehudah 2:20]
  2. Halachic day and night correspond to periods of daylight and darkness, irrespective of how short or long they are. For example, at the actual North Pole, Halachic day and night lasts for six months each, with the entire “day” lasting a full year. Accordingly, Shabbos occurs every seventh year. [Similar to the position of Minchas Elazar 4:42]
  3. Halachic day and night occurs every 24 hours, but determining the start and end times are a matter of intrinsic and irresolvable doubt. [One possible way of understanding the Mor uKetziah]
  4. Halachic day and night occurs every 24 hours even at the Poles, and their start and end times are determined independently of daylight and darkness. [Tiferes Yisroel]

The first three approaches have not gained significant Halachic traction, and the vast majority of authorities subscribe to the Tiferes Yisroel’s model. However, this approach raises an obvious question: If Halachic day and night is determined independently of daylight and darkness, then what does determine it? At what point does Halachic day and night begin and end? Here, too, there are many opinions, and they can be collected into two general schools of thought:

The first school of thought believes that the beginning and end of Halachic day and night is determined by factors independent of one’s current geographical location. This includes the following opinions:

  1. Halachic day and night begins and ends at the same times as in Israel. [Teshuvas Divrei Yatziv, OC 108:11]
  2. Halachic day and night begins and ends at the same times as one’s primary residence. For example, a Melbournian visiting the South Pole will observe his Halachic day and night at the same times as Melbourne, whereas a New Yorker visiting the South Pole will observe his Halachic day and night at the same times as New York. This can lead to the enigmatic situation where two seatmates on the same ship can simultaneously observe very different Zmanim. [One possible way of understanding the Tiferes Yisroel]
  3. Halachic day and night begins and ends at the same times as one’s last port of departure. For example, being that the DansDeals Cruise departed from Ushuaia, all Zmanim would be calculated as per Ushuaia. This can lead to the enigmatic situation where the passengers of two cruises with different embarkation points will observe very different Zmanim even when they are right next to each other. [Another possible way of understanding the Tiferes Yisroel]
  4. Halachic day and night begins and ends at the same time as it does in the closest place that experiences regular 24-hourly phases of daylight and darkness. [A third way of understanding the Tiferes Yisroel]

The second school of thought maintains that Halachic day and night determinations must depend on events at one’s current geographical location. This includes the following opinions:

  1. Halachic night will exist for a split second during the Polar day and Halachic day will exist for a split second during the Polar night. [Mo’adim u-Zemanim 2:155]
  2. Halachic night and day will span twelve fixed hours each, similar to night and day at the equator. The midpoint of Halachic night will coincide with solar midnight and the midpoint of Halachic day will coincide with solar noon. [The most straightforward way of understanding the Ben Ish Chai in Teshuvas Rav Pa’alim – Sod Yesharim 2:4; one possible way of understanding the opinion of the Lubavitcher Rebbe in Igros Kodesh Volume 2 page 94, Toras Menachem 5746 Vol 2 page 847]
  3. Halachic night and day will span twelve fixed hours each, with the beginning of Halachic night coinciding with solar midnight and the beginning of Halachic day coinciding with solar noon. [Another possible way of understanding the opinion of the Lubavitcher Rebbe, ibid]

With the plethora of opinions, and the diverse range of Jews on the cruise who would be following different Poskim, I immediately reached out to Dan about this issue. However, a quick discussion and examination of the route’s map clarified that the cruise would not be entering the Antarctic Circle, rendering the whole issue moot. So, that was the end of that. Or, so we thought…

Why wasn’t’s Zmanim Calculator working?

Several weeks later, Dan was compiling Zmanim for the cruise. Since the route could change based on a number of factors, it was necessary to plan for all eventualities. Dan noticed that’s Zmanim calculator seemed to lose some numbers south of 65°6’. From that point on, it was not providing some Zmanim which depend on Shaos Zmanios (such as Plag Hamincha), even though it was providing times for sunrise and sunset until 65°51’. Dan reached out to me about this.

It turns out that there was good cause for this dichotomy: There are various opinions in Rishonim regarding the definition of Shkiah. The most-widely practiced opinion, generally known as Shkias HaGeonim, defines sunset as the sun descending below the horizon. According to many authorities, this refers to the moment that the disc of the sun completely disappears from the horizon. However, the Alter Rebbe (first Lubavitcher Rebbe), author of Shulchan Oruch HaRav and the Baal HaTanya, has a unique understanding of Shkias HaGeonim. His position is clearly spelled out at length in a treatise entitled “Seder Hachnosas Shabbos”, a masterful Pilpul of the relevant Sugyos in Gemoro and Rishonim. The Alter Rebbe refers to visible sunset at Shkiah Haniris, but demonstrates that Shkiah Amitis, true Halachic sunset, occurs a short time later, when the sun is about 1.5-1.8° below the horizon, for that is the time when the trailing edge of the sun’s disc is no longer visible on the horizon to an observer standing on the mountains of Eretz Yisrael.

This explains why was losing some numbers south of 65°6’, for although the sun visibly sets in those areas, it does not descend to 1.583° below the horizon (the figure used by If so, why was still displaying sunrise and sunset times? It is accepted Chabad practice to abide by visible sunset as a stringency, and Shkiah Amitis is generally not relied upon. For example, daytime mitzvos are to be completed before visible sunset, and one should begin Shabbos prior to visible sunset. For that reason, Shkiah Amitis is intentionally not published on

Nevertheless, uses true sunrise and sunset to calculate Shaos Zmanios, which is why Zmanim that depend on Shaos Zmanios were not displaying south of 65°6’. [Although this is the default setting of, it must be noted that there is some debate among Chabad Rabbonim regarding this matter. Therefore, provides the option of customizing the settings to calculate Shaos Zmanios based on visible sunrise and sunset instead. Consult your Rav for further guidance.]

What is the definition of continuous daylight?

Although we could now understand what’s software was doing, it turned out to be the catalyst for a series of new questions:

  1. Although the plan was for the ship to remain north of 65°6’, it was still within the realm of possibility that the ship would veer south and be positioned between 65°6’ and 65°51’. This meant that there was a chance that the ship would be in a place with visible sunrise and sunset, but without Zricha Amitis and Shkiah Amitis. Compounding the problem was that this was most likely to occur either on Friday or Saturday, i.e. right around Shabbos.

If the ship were to veer into this area, what would it mean for those who follow the opinion of the Alter Rebbe? Since true sunset wouldn’t occur, the day would be uninterrupted by night, and one would now have to adopt a “Polar Zmanim model” (i.e. the way Zmanim are calculated in the Poles). This would be further complicated by the fact that most of the passengers were not Lubavitchers, and would not be following the opinion of the Alter Rebbe. They would therefore retain the “Standard Zmanim model” (i.e. the way Zmanim are typically calculated), with Shabbos beginning at visible sunset (around 11:45pm Friday), or as early as Plag Hamincha (around 10:00pm Friday) and ending at Chatzos (around 1:10am on Sunday). Could the Lubavitchers follow this too, or would they have to switch to a “Polar Zmanim model” and keep separate Shabbos times from the rest of the group?

  1. This, quite naturally, led to the next question. It is generally accepted that sunset is not the true end of the Halachic day. Rather, this happens at some unknown point during Bein Hashmashos. According to all eventualities, the ship would definitely be positioned in a place where Tzeis Hakochavim does not occur. If so, an argument could be made that all the passengers would be in a doubtful situation: Since only part of Bein Hashmashos elapses, but not all, perhaps there is night, but perhaps not. If there is night, the “Standard Zmanim model” must be used, and if there is no night, the “Polar Zmanim model” must be used. Since this would be a situation of doubt, all the passengers on the ship would now have to be stringent and adopt the stringencies of both the “Standard Zmanim model” and “Polar Zmanim model”. This would be doubly confounded by the amount of options there are for the “Polar Zmanim model”, and further compounded by the fact that many of the results would be mutually exclusive. For example, Licht Bentchen would be close to midnight according to Standard Zmanim, but before 6pm true solar time according to the Ben Ish Chai’s Polar model. This leads to a conundrum: If you light before 6pm, this will be way too early if the Zmanim do in fact follow the Standard Zmanim. If you light shortly before midnight, this will be way too late if the Zmanim do in fact follow the Polar Zmanim model of the Ben Ish Chai.

A starting point for dealing with this last question is a fundamental Biur HaGra (OC 261:2) where the Vilna Gaon sets forth his rejection of Rabbenu Tam’s opinion regarding sunset and nightfall. For the purposes of this article, there is no need to get into all the details of Shitas Rabbenu Tam here, other than this one: Rabbenu Tam (as understood by the Vilna Gaon) holds that Tzeis Hakochavim does not occur until the sun descends 16.1° below the horizon. The Vilna Gaon notes that, in Vilna, the sun does not descend 16.1° below the horizon for about four months in the summer. If Rabbenu Tam were correct, that would mean that there is no (definite) night for four months in Vilna. Since the Vilna Gaon found this too problematic to accept, he therefore rejected the opinion of Rabbenu Tam. This point is extremely relevant to our discussion, because the Vilna Gaon is asserting that there is no (definite) Halachic night in a place where there is sunset but no Tzeis, and the day remains (potentially) continuous. According to this approach, all the passengers on the ship would indeed find themselves in a predicament where they would have to adopt the stringencies of both the “Standard Zmanim model” and “Polar Zmanim model”, with all the difficulties this entails.

Yet, there is a flipside. Although we have clear evidence regarding the Gra’s position on this issue, his very proof would serve to demonstrate that other Poskim disagree. In other words, all the Poskim in Vilna and other northern cities who embraced Rabbenu Tam’s opinion, yet accepted that the summer was not one long uninterrupted day, would be bound to hold the exact opposite of the Gra on this point. They would have to somehow hold that, where there is sunset but no (definite) nightfall, the days are somehow not regarded as continuous.

In support of this, it must be noted that many Poskim who discuss the North Pole issue clearly use sunrise and sunset in their terminology, implying that they delineate the boundaries of day and night. What could the explanation for this be? It might be suggested that, in the absence of Tzeis and Alos to serve as the boundaries of day and night, sunrise and sunset become the new markers instead. If this were correct, then this would discount both of the issues raised above (i.e. the lack of Shkiah Amitis and Tzeis), and all the passengers on the ship could just calculate the beginning of Shabbos as per visible sunset and the end of Shabbos as midnight. [This explanation can be gleaned from Teshuvas Rav Pa’alim – Sod Yesharim 2:4; a similar idea is propounded in Teshuvas Divrei Yatziv, OC 108:11.)


In summary, the cruise highlighted the following difficult Halachic questions:

  • How are Zmanim determined in the Poles?
  • If a region experiences Shkiah but not Tzeis, is it regarded as a Polar region?
  • If a region experiences Shkiah Haniris but not Shkiah Amitis, is it regarded as a Polar region?
  • Are Shaos Zmanios calculated according to Shkiah Haniris or Shkiah Amitis?

What was the practical conclusion?

Well, the cruise ship ultimately remained north of 65°, and everyone lived happily ever after. Until next time.

This discussion represents a fraction of the underlying issues, compressed into something which is hopefully readable to you. It also provides a small glimpse into the huge amounts of time and energy Dan and Moishie invested into just one detail of the Cruise.

Stay tuned for the article about Polar flights and for further discussion about what would have happened had the boat traveled further south than 65°6’.

Leave a Reply

31 Comments On "Guest Post: Halachic Zmanim In Polar Regions On The Kosher Antarctica Cruise"

All opinions expressed below are user generated and the opinions aren’t provided, reviewed or endorsed by any advertiser or DansDeals.


Dan I didn’t know you were a Talmid Chachaum. Good to know


Very thorough, fascinating, and unique halachic scenarios, Rabbi. Unfortunately, there may be some who will strongly disagree and argue with you in this forum (but it’s safe to say that you didn’t just spend 5 minutes typing up some halachic comments, but spent a considerable amount of time in Halachic research). The timeless classic version for years was the zmanim question in Hawaii. Not to go too off topic, I too am fascinated by “wacky” halachic scenarios- such as a Shabbos Shacharis minyan of 9 Cohannim and 1 Yisroel (who gets which Aliyah?) Or a Yomtov morning minyan with only Cohannim (if everyone is doing Birchas Hakohanim- who is responding Amen?). Good stuff…

EY (or non-Ashkenazim)

Lav davka YT (per my temp screen name) – to the last one.

Also, this would already be resolved by some opinions on the less-“wacky” scenario of a Kohen being Shliach Tzibbur (and using a siddur in doing so, “wacky” as that may seem).


I’ve never “heard” that one of Kohen being Shliach Tzibbur and using a siddur. What’s the deal with that? Over this past shabbos I was sitting next to a couple guys talking about past vacations through the decades (one of which was a Cohen), and we were talking about if he can visit the Pyramids in Egypt (dead bodies in the Pyramid, one of the wonders of the world).

EY (or non-Ashkenazim)

Using a siddur being a possible rationale for the Shliach Tzibbur (regardless of yichus) answering – rather than our being concerned that he’ll lose track of which bracha they’re (and in prompting them, he’s) up to.


The reason for the SHa”TZ not doing Birchas Kohanim is out of concern that he’ll lose his place and not be able to continue leading. Now that we have siddurim this is not as big of an issue, and is permitted. M”B (128:20) suggests doing do if the SHa”TZ is the only Kohein, but if there are others they can duchan and he doesn’t (but in Be’er Heitev he quotes Pri Chadash that he can if he has a siddur).


Thanks so much for this Main Site post.


Hi Dan, great post!
Couple of things here though that I find bizarre:

1. You translate a couple of Hebrew words at the beginning of the post. I thought that was funny, because you translated only a select few words, not sure why those few were lucky to get translated (like Halachik). If you want to translate, be consistent and translate all of it. If you don’t want to translate, why translate those few words? Not important, just thought it was weird.

2. Inside the article, I find it extremely bizarre that a whole section is dedicated to questions on’s zmanim, as if it’s the Urim v’Tumim! Lol. They are not a divine machine, the people who set it up are all alive, you can ask them your questions, you don’t have to make a rashi and tosfos on why their set of zmanim respond a certain way etc. They are not perfect, far from it, nobody is perfect, it’s impossible to be. Many also don’t accept it, in fact many within the Chabad community itself dispute their methodologies. I just this was bizarre. Same thing would be if you had your shayla on MyZmanim’s calculation..


Fascinating read. Looking forward to the article on polar flights.


So with you not having to overstress since you were north of 65°, what time did Shabbos start and end where you were and how long was your fast?


Thanks for the very nice article.
And thanks for reassuring us that more trip notes are on the way…. Waiting to see shots of the dinner plates etc.
(Unless the drake shake situation didn’t allow for good shots?..)


Yashar Koach for the writeup! this is an interesting topic and it’s wonderful that you use this platform to teach about Halacha in such a positive way. Hatzlach Rabba in all that you do.


Thank you Dan for allowing people to argue and get their heart rate elevated on something that they will never experience.


Torah hee, ulelomdah ani tzorich. The tiferes yisroel weighed in on it, knowing he’d never be there, either.

Jack out of the Box

This past summer (beginning of July) I spent a (very short) night in Glasgow (55.8642° N). When I arrived at around 11pm it was still twilight. After dinner my host gave me a brief tour of the city and before returning home when it was about chatzos he pointed to the north and noted to me that the sky was not darkened over there. By the time I got to bed a short time later, it was getting light outside.
A few days later I was in Helsinki (60.1699° N) for a 7-hour layover between flights. I welcomed the opportunity to explore a location I had not yet been. However, in choosing my flights I was careful not to remain in Helsinki “overnight” because although there is sunset there, according to most opinions there is no tzais on that day which would cause unnecessary safek regarding krias shemas shel arvis. There is an Orthodox community in Helsinki but I myself had no need to remain in Helsinki overnight so I chose to stay clear of questions.
I was actually quite curious what Dan’s cruise would do about these issues and I am very impressed by the thoroughness of his halachihc and geographic research.


Thanks dan. Waiting for the rest of trip report. Maybe we can have a write-up regarding Interesting shaalos (halachik questions regarding flying and traveling.
For eg.
Storing food under the seat, which someone is sleeping on.


Wow. Never thought about that. I put my personal bag, with snacks, under the seat in front of me all the time… So is a chair considered a bed, and if it’s on a plane is it considered ground…


Nice! Thanks.


I enjoyed this! Thank you


Very interesting! Thank you very much for posting this.
Please continue with this type of content, of course in addition to everything else you post 🙂


Nice post. Dan your the men.


I think you should start a series on halacha while traveling shaylos.

ben ish chai

Dan, as in every subject, through & comprehensive job !


Would you consider having a write up on Alaska and Hawaii? Perhaps Rabbi Shmuel Lesches would be willing to address the relevant (Zmanim) Halachos, as many people travel there and would be a big toeles. TY


Dan, great write-up! יישר כחך to Rabbi Lesches on the “shiur.”
I think further posts on halachic issues of travel (that go beyond the perpetual daven-at-your-seat-or-the-back-of-the-plane or should-ElAl-accommodate-seat-switch-requests-to-avoid-men-and-women-sitting-next-to-each-other debates) would be both very interesting and helpful. I hope to see more in the future.
This reminded me that I’ve been meaning to suggest a post with recommendations for flights based on the ability (or likelihood) of davening with a minyan before or after, for those non-Israel or NY flights that are unlikely to have a minyan on board.