Date Line In Halacha

The Dateline in Halacha

The subject of the Dateline in Halacha has been studied extensively during the past few decades and much has been written on the topic. The two overriding questions dicussed are

  1. Does Halacha recognizes the International Dateline, and if not, where is the Halachik dateline..
  2. Are Halchaos affected by one’s merely crossing the Dateline.

These issues have been discussed extensively in the Sefer Taarich Yisroel by Rav Yisroel Taplin printed in 1997, and the English condensed version of the sefer, The Dateline in Halacha published in 1999. Insofar as this book is no longer in print, it had been included in this website.

The most frequently asked questions that arise today however center around transpolar flight. In most cases the Dateline is crossed, resulting in great confusion as it relates to Halacha. The primary focus of this website is to address this issue, but as stated above, for anyone wishing a better understanding of the subject matter, The Dateline in Halacha has been appended.

Transpolar Flights and Halacha

Before we begin our analysis of the halachik issues raised during transpolar flight, it is important to gain an appreciation of what transpires during the long flight from both the halachik and geographic perspectives.

Rabbi Yisroel Taplin, senior member of the BMG Kollel in Lakewood has written an extensive 800 page sefer on the topic of Halacha and the date line. In 1999 I wrote an English synopsis of many of the conclusions that he reaches entitled The Dateline in Halacha, and it is not the purpose of this essay to write a synopsis of the synopsis. We will rather attempt to draw on the conclusions of The Dateline in Halacha and apply them to transpolar flights, something which did not exist at the time of its publication.

Halacha and the Dateline

Crossing the Dateline can affect Halacha in many areas. We will focus only on the most frequently asked questions, Shma, Tefila, Tefilin, Shabbos, and fasts. Halachik questions that arise less frequently such as crossing the dateline during SefirasHa’omer, Shiva or Shiva Nekiyim, or a baby that crosses the dateline before reaching his eighth day, have been addressed in The Dateline in Halacha.

Two overriding global matters affect many aspects of the analysis of almost every question that arises; the location of the dateline, and what halachos if any are triggered by merely flying over the dateline.

The Location of the Dateline

There are three primary opinions as to the location of the Dateline

Rav Yechiel Michel Tukatzinsky- The line is located 180 degrees away from Jerusalem at approximately the 145.2W meridian. (more in this later)

Baal Hamaor - The line is located 90 degrees east of Jerusalem at approximately the 125.2E meridian. The Chazon Ish adopts this opinion but modifies it slightly where the 125.2 meridian cuts through a landmass. This is discussed in greater detail in The Dateline in Halacha.

Rav Isser Zalman Meltzer- There is no official Halachik Dateline, and we adopt the International Dateline which is accepted by world convention.

In this essay we adopt the opinion of Rav Y.M. Tukatzinsky as this is the opinion of most poskim, though where questions of D’Oraisa mizvos are concerned, we consider the opinion of the Chazon Ish as well.

Crossing the Dateline

Do we consider the crossing of the Dateline which is invisible to us as the determinant as to when the obligation for performing specific mitzvos are created, in other words are mitzvos day/date sensitive?


Does one’s experience of a sunrise or sunset trigger the obligation to perform specific mitzvos?


Are different mitzvos treated in different ways.

Most poskim feel that most mitzvos are day/date sensitive and crossing the dateline midday can trigger obligations. Among poskim who share this opinion are Rav Moshe Feinstein, Rav S.Z. Auerbach, Rav Chaim P. Scheinberg, Rav Ovadia Yosef, and ybl”c Rav Chaim Kanievsky and Rav Yechezkel Roth.

Other prominent poskim who feel that in order for one to be obligated to perform certain mitzvos, i.e. Tefila, one must actually experience a new personal day, the second opinion noted above, are the Betzel Hachochma and Rav Elyashiv.

For the purpose of this essay we have adopted the first position as it seems to be the majority opinion, but one should consult with one’s local posek for definitive direction.

Nevertheless, we must analyze each mitzvah separately as not every mitzvah falls neatly into any single category.

Tefila and Tefilin

Tefila and Tefilin are date sensitive. Hence, when one crosses the dateline midday in a westerly direction, when the day gets pushed forward - Monday becomes Tuesday- one must treat crossing of the dateline as if it were a new day. If local time is morning, one must daven shacharis again even though he may have davened Shacharis only a few hours earlier. Similarly, one must put on tefilin again as it is a new day. If one crosses the dateline when local time is afternoon, one must daven mincha on this “new” day, and put on tefilin as well.

On the other hand, when crossing the dateline in an easterly direction, when the day moves backwards, Tuesday becomes Monday, one need not repeat Tefilos already recited on the Monday experienced before crossing the dateline, as for this individual, this is a second Monday. We will see how this applies in practice later in the essay.

Note 1: This follows opinion 1 mentioned above. Rav Elyashiv would disagree

Note 2: Although when one repeats a day, there may be no “obligation” to daven a second time, one may certainly say the Shemoneh Esrei after experiencing a new sunrise or sunset at the appropriate time for each Tefila as Nedava.

Note 3: If one opts to daven Shemoneh Esrei as Nedava, one may not say Birchos Krias Shma or Pesukei Dezimra as Nedava.

Note 4: If one repeats a day, although there may be no technical obligation to wear tefilin again after seeing a new sunrise, one should preferably wear Tefilin again.

Krias Shma

Even the opinion that feels that Tefila is day/date sensitive will hold that Shma has different parameters as to when the obligation is formed. The proper time for Shma is stated in the Torah, Beshochbecha U’vekumecha, when you lie down to sleep and when you arise in the morning. Nightfall obligates Krias Shma shel Arvis, and daybreak obligates Krias Shma shel Shacharis. Hence, even if one repeats a day, a new sunset and sunrise will trigger a new Shma obligation according to all opinions.

Birchos Hashachar

Here too, experiencing a new sunrise is what obligates one to make these brachos. Birchos Hashachar are blessings of praise for all the gifts given to us on a daily basis; our senses, the ability to think and to walk upright. A new daybreak is what prompts this obligation. These brachos are not day/date sensitive.

Note: There are dissenting views- I refer specifically to Rav Yechezkel Roth who is of the opinion that these brachos are in fact day/date sensitive. But this is not the majority opinion.


All would agree that Shabbos is determined by the day/date and is not dependent on one’s experiencing seven sunsets.

Fast Days

Fast days commemorate events that happened on specific days. Clearly, these days are day/date sensitive, similar to Shabbos. Therefore, if one crosses the dateline midday in a westerly direction, where Monday (the fast day) becomes Tuesday (a non fast day), logic would dictate that one may break the fast upon crossing the dateline. This in fact the opinion of Rav Chaim P. Scheinberg. Other poskim, among them Rav Elyashiv and Rav Chaim Kanievsky disagree. Their opinion is based a Gemara in Taanis 12 which states in the name of Rav Chisda, that any fast day that did not see a sunset is not a fast day. Hence, if Monday becomes Tuesday while the sun is still shining, the fast cannot end until sunset. Fast days according to this opinion are unique.

Transpolar Flights

My first trip to the Far East was in 1976 on a Pan Am flight to Tokyo via Anchorage. I sat next to a seasoned traveler, an Orthodox man about 30 years my senior who was a camera importer from Japan. He explained to me what a pleasure it is to travel on a wide bodied jet which had been introduced only a few years earlier. His first trips to the Far East in the early 1950s were on turbo props that made quite a few stops along the way, had a cruising speed of about 300 mph, did not deal well at all with turbulence, took well over a day door to door, and a day or two to recover from the ordeal.

I subsequently met a much younger man, a member of the Syrian community from Brooklyn who described to me how in the 1920s his grandfather would travel to San Francisco by railroad, and then board an ocean liner to Shanghai. A typical buying trip could take 6 months. Travel time alone on the ship round trip was a few weeks including a few days in Honolulu on the return trip to recuperate.

In 2016 we truly cannot relate to this. If our 13 hour nonstop flight to Beijing aboard a Boeing 777 stays an extra half hour on the tarmac, we get edgy. Nonstop has become the standard, and with it has introduced the Orthodox traveler to a new set of issues as they relate to transpolar travel and Halacha.

Polar Travel Routes

Travel to the Far East from the United States has taken on an entirely new characte r since the publication of The Dateline in Halacha in 1999. Much of what was written at that time with regard to how mitzvos are to be observed during the flight, has become obsolete with the advent of the adoption of the transpolar route by the airline industry.

Routine transpolar flight became possible after the end of the cold war, when the U.S. and Russia adopted new policies of allowing commercial flights over each other’s territory, and with the development of planes like the Boeing 747-400 and Airbus A340, with ranges of about 9,000 nautical miles.

Transpolar flight reduces flight times by as much as three hours, Transpolar flights are smoother with less turbulence in the polar region, more cost effective, and environmentally preferred because of reduced fuel emissions. In 1999 United Airlines flew 12 polar demo flights. By 2006 the total for all airline polar flights exceeded 5000.

Travel via transpolar route may affect halachik practice during the flight. Prior to the introduction of the transpolar route, most flights from New York to the Far East stopped in Anchorage for refueling and a crew change. Anchorage is in the sub Arctic region. Today however, since part of the flight takes us through the polar region, where times zones are so compact and shifts in daylight hours between summer and winter are so extreme, there is no simple one-size-fits-all method of approaching halachik issues. Each case must be individually studied. However, in order to gain an appreciation for what issues may arise, a basic understanding of what transpires from a geographic/halachik perspective during such trips is in order.

A Geography Primer

It is almost impossible to understand the Halachik challenges posed by a transpolar route without reviewing high school geography, a subject many may have found distasteful back in ninth grade, but essential for trying to grasp the Halacha. We have to reacquaint ourselves with how one’s latitude has an effect on seasons and the number of daylight hours at a particular location, and how one’s longitude determines day/date and the hour of the day at any particular location.


Latitude, otherwise known as parallels, are lines that run on the map horizontally. The Equator is the 0 parallel, while the North Pole is at 90 degrees north. Each degree in latitude measures about 70 miles, so the distance between the Equator and the Pole is approximately 70 X 90 = 6300 miles. Latitude measurements of some common cities: Miami (26 North), Jerusalem (32N), New York (40N), London (51N), Anchorage (61N), Beijing (40N), Hong Kong (22N).

The latitude and the time of year determine the time of sunrise and sunset, the length of the day, at each location in the world. The further one gets from the Equator, the wider the range of the gap between sunrise and sunset

Date Sunrise Sunset Length of Day
Miami (26N) Sep 25 7:10 7:14 12 h 4 min
Dec 7:05 5:36 10 h 31 min
Jun 6:31 8:16 13 h 45 min
New York (40N) Sep 25 6:47 6:49 12 h 2 min
Dec 7:18 4:34 9 h 6 min
Jun 5:26 8:31 15 h 5 min
London (51N) Sep 6:52 6:53 12 h 1 min
Dec 8:05 3:56 7 h 51 min
Jun 4:44 9:22 16 h 38 min
Anchorage (61N) Sep 7:51 7:51 12 h 00 min
Dec 10:16 3:44 5 h 28 min
Jun 4:22 11:43 18 h 21 min
Reykjavik, Iceland (65N) Sep 7:19 7:19 12:00
Dec 11:23 3:32 4 h19 min
Jun 2:57 12:02 21 h 5 min


The vertical lines on the globe are longitude lines. When traveling in an east-west or west-east direction, you are changing longitude. Longitude is measured by 360 vertical lines that go from the North Pole to the South Pole. However, unlike latitude, longitudinal lines are not parallel to each other. At the equator, the widest point of the Earth, which measures approximately 25,000 in circumference, the distance between each longitude degree is approximately 70 miles. As you move away from the equator toward the poles (as latitude increases), the circumference of the Earth decreases to the point where all 360 longitude degrees converge at the Poles, and the distance between longitude lines is reduced to zero.

Geographers have set up a system of plotting points on the globe using longitude and latitude coordinates.

As we mentioned above, latitude degrees are measured by their distance from the Equator with the Equator (the midpoint between the North and South Poles) being the zero degree mark. As you go north or south away from the Equator, each 70 miles adds one degree to your latitude, until you reach the pole at 90 degrees north or south.

Unlike latitude, longitude has no natural starting point. International convention has determined that the city of Greenwich in England be the starting point at zero degrees, and as you move west toward the Americas, the longitude lines are noted to be West, while as you move east toward Asia, the longitude lines are noted to be East. New York lies at the 74 degree West longitude, the 74W meridian, while Jerusalem is at the 35 East meridian. Hence, the longitudinal spread between New York and Jerusalem is about 109 degrees.

The East and West longitude points meet at the 180 degree mark. There are 180 degrees east and 180 degrees west. Together, you have the full 360 degrees of the circle.

The 0 longitude point in Greenwich is called the Prime Meridian, while the 180 degree point is called the AntiMeridian. This point is the International Date Line (IDL), the point at which the day/date moves forward as you cross it in a westerly direction, and the day moves backward as you cross it in an easterly direction. (Note: While the 180th meridian should in theory be the IDL, and for the most part it is, for convenience sake, world convention has made provisions for the IDL to zigzag around country borders so as not to have the Dateline run through a single landmass).

Time Zones

When it is noon in New York, it is 9 AM in Los Angeles and 7 PM in Israel.

The world is divided into 24 time zones, each one measuring 15 longitude degrees (360/24=15). Los Angeles is 3 times zones to the west of New York, while Israel is 7 times zones to the east. As we mentioned above, New York is about 109 degrees west of Israel. Divide 109 by 15 and the result will be slightly more than 7.

Travel through Time Zones

Let us take the simple long distance flight with which most of are quite familiar; the trip from New York to Israel and back.

When we leave New York on the El Al midnight flight, we are in the air approximately 10 hours, yet we land at about 5 PM local time which is in fact 17 hours later. Our watch has so-to-speak moved 17 hours in only 10 hours. That is because we traveled over 7 times zones in the easterly direction. As the sun travels in the sky from east to west, we traveled against the sun, advancing seven time zones.

On the return trip we have the opposite experience. The 1 AM flight from Israel which takes about 12 hours to reach New York lands at about 6 AM New York time. In 12 hours our clock moved only 5 hours. That is because we crossed 7 times zones in a westerly direction, flying “with” the sun.


In the same way that latitude affects the length of day, the amount of time between sunset and darkness, twilight or Bein Hasehemashos, varies greatly as well.

The U.S. Naval Observatory divides twilight into 3 segments.

Civil Twilight: the time at which the sun is 6 degrees below the horizon. At this time, there is enough light for objects to be clearly distinguishable and that outdoor activities can commence (dawn) or end (dusk) without artificial illumination. Civil twilight is the definition of twilight most widely used by the general public.

Nautical Twilight: the time when the center of the sun is 12 degrees below the horizon, and only general or vague outlines of objects are visible. During the evening this is when it becomes too difficult to perceive the horizon, and in the morning this is the point when the horizon becomes distinguishable. This term goes back to the days when sailing ships navigated by using the stars.

Astronomical Twilight: the time at which the sun is 18 degrees below the horizon. It is that point in time at which the sun starts lightening the sky. Prior to this time during the morning, the sky is completely dark. During the evening, this is the point where the sky completely turns dark.

The Halachik definition of twilight is difficult to pin down. In broad strokes, some opine that the time of Alos Hashacha, daybreak, or Tzeis Hakochavim, nightfall is a fixed number of 72 minutes before or after sunrise or sunset respectively, regardless of location or date. Others feel that the amount of darkness perceived, defines Alos and Tzeis. For a study of this subject I refer you to an excellent book recently published, Dvar Yom by Rabbi Dovid Braunfeld , where he discusses the topic at length.

The reason why I even broach this issue, is because when one is in flight, the sky is in a twilight state for much longer periods than we experience at sea level, especially at extreme latitudes. Trying to figure out just what one sees can be a challenge.


The Talmud Shabbos 118 raises the issue of the effect of altitude on the time of sunrise and sunset. Tverya was in a valley while Tzippori was in the mountains. The gemara indicates that we may take altitude into account. The consensus of opinions among the poskim is that while we do take altitude into consideration when determining zmanim on land, i.e. mountains vs valleys, when dealing with altitudes above land, i.e. in airplanes, we consider only the times that apply to ground level.

Altitude can have drastic effects on the times of sunrise or sunset. At the latitude of New York (40N), at 35,000 feet above sea level, the typical altitude of most planes in flight, sunrise is between 20-24 minutes earlier than at sea level. But as we approach higher altitudes (60N), the range is much greater. In September sunrise at 35,000 feet is 31 minutes earlier than at ground level, while in June it is almost 2 hours earlier.

At the 70th parallel in December, the sun may not rise at all at sea level, while at 35,000 the sun can be seen above the horizon.

I bring these issues to the attention of the reader to simply raise awareness that visual sighting of light or darkness cannot always be taken at face value when determining halachik obligations. There is much discussion among the poskim.

The Arctic Region

As is evident from the above, higher latitudes engender extreme variances in day length. In Iceland, which is only about 2 degrees below the Arctic Circle, the day length can be as short as 4 hours in December, or as long as 21 hours in June. As you go above the Arctic Circle (66.5N), there are days during the summer when there is no sunset at all, and days during the winter when there is no sunrise. The higher the latitude, the greater the number of days that fall into this category. At the North Pole, the sun rises in March and sets in September. Day length is 180 days. At the 80th parallel, there are about 130 days of daylight. At the 70th parallel the number of daylight-only days is about 70.

The inverse is true during the winter months, from September to March. There is no daylight for the equal amount of days at each respective latitude point.

Needless to say, without time demarcations of sunrise and sunset, it is difficult to determine zmanim. It is beyond the scope of this essay to address any issues in this region. Insofar as much of the transpolar trips take place in this region, it is important to get a basic understanding of just what one sees when looking out of the window. It could be midnight and the sun could be high in the sky, or it could be noon and the stars are shining bright, all dependent on the date and the latitude.

Flight Paths, Time Zones, and Halacha

The shortest distance between two points is a straight line.

When planning a flight path for air travel, the navigator must consider factors other than mileage, i.e. weather conditions, air traffic control, etc. There may be several different routes for pilots to choose when plotting their flight plans. During certain times of the year a pilot may choose a more northerly route, at other times a more southerly route. The guiding principle is to reach the destination in the shortest amount of time while trying to conserve fuel as much as possible.

Before attempting to address the transpolar routes to the Far East, let us first take a case study of a far simpler flight, one that is far more common.; the New York – Tel Aviv flight.

Flight Paths

If you have ever watched the screen during a flight from New York to Israel, you will note that at times the plane may fly in a more northern path over England and northern Europe. At other times you might notice the plane flies a few hundred miles to the south, over Portugal and Spain.

The latitude of New York is 40. Israel’s latitude is 32. Logic would dictate that the flight take place between the 32nd and the 40th parallel. However that is not the case. The route may frequently take the plane as high north as the 55th parallel.

To the passenger, the difference in flight paths or time of year is not noticed, unless one is concerned with the local time at any particular point during the flight, and its effect on the proper times to daven or recite Shma.

Polar Routes

Having studied what happens during a relatively simple flight from New York to Tel Aviv, where the whole flight takes place in the temperate zones, we can now embark on a far more complex study of polar trips, as we investigate the potential halachik issues as we pass through extreme geographic zones.

Longitude lines converge at the Poles. So while the distance between each longitude degree measures about 70 miles at the Equator, as you move closer to the Poles, longitudinal degrees get smaller and smaller.

Latitude Distance Between Longitude Degrees

In practical terms, a plane traveling at 500 mph from East to West at the 40th parallel, a New York to California flight, will cross only about 10 longitude degrees, or about 2/3 of a time zone in each hour.

On the other hand, if the flight path were within 300 miles of the North pole (the flight path of many flights to the Far East), that would mean that a plane traveling at 500 mph at the 85th parallel, would cross 100 longitude degrees or about 7 time zones in a single hour!

Needless to say, this could have possible Halachik ramifications. Because of the Halachik complexities of dealing with the polar region, in our study we will for all intents and purposes suspend Halachos affected by time in these extreme circumstances, But an understanding of what transpires during the flight, and the ramifications of these changes upon re-entry into a more “normal” environment is important.

Polar East or Polar West

We think of China being to our west, that is to the left on a flat map of the world. However, if you look at the world from the North Pole, we could draw a straight line from New York to China that goes north to the pole and then south from the pole. If you flew directly north from New York at the74W meridian, continues into the 106E meridian after crossing the Pole. (Beijing and Hong Kong at about 113E). So the most direct route would be to go directly north with only a slight nudge to the west to compensate for those few degrees.

There are many factors that determine a pilot’s particular route; wind speeds, weather conditions, etc. At times the pilot may choose to fly just west of the pole, while at other times he may choose to fly east of the Pole.

Stand above a globe looking down at the North pole. If you drew an almost straight line from NY to Beijing just to the left of the pole (west), you would cross the Antimeridian, or the IDL. Draw an almost parallel line but this time drag it just to the right of the Pole (east), and you never crossed the dateline at all. (See Map 1)

While in reality these two routes are quite close to each other, within a few hundred miles, as you look at these flight paths on a flat map of the world, the western route which crosses the date line looks like it is flying high over Alaska, the Bering Straits and Eastern Siberia (See map 2) .The easterly route looks like it is flying over Northern Europe, Finland, Russia, and Western Siberia (see map 3). The screens on planes showing your location during flight, reflect this reality but from a different perspective. The maps that are shown on the planes do not show a polar view but rather a flat view. On some flights the map shows you flying over Alaska (See Map 4), while on other flights to the same location, the map may show that you are flying over Finland (See Map 5). In reality, in the Arctic region, where all longitudinal lines converge, the distance between these points is not all that far apart.

You take off and land at the same time. On the easterly route you are flying east through many time zones with the clock racing forward, so that local time at destination (Hong Kong) after a 16 hour flight, will be 28 clock hours after takeoff. On the westerly route, your time falls back 12 hours and then fast forwards 24 hours upon crossing the dateline, netting you the same 28 clock hours.

Flight details

The Northwest route (NW) leaves NY flying almost directly north toward the pole. During the first 5 hours of the flight, the longitude veers ever so slightly westward, and you have moved only one time zone backward, from Eastern Standard Time (GMT -5) to Central Time (GMT -6). During this time, when you are about 4 hours into the flight, the Arctic Circle is crossed. You will remain in the Arctic region until the 10th hour of your flight, when you re-enter the sub-Arctic region.

If we so-to-speak stop the clock when you enter the Arctic, and restart it 6 hours later when you re-enter the sub-Arctic, where conventional halachik zmanim come into play, your clock will have moved forward by about 21 hours. More correctly, it will have moved backward in time by 3 hours and catapulted 24 hours forward as you cross the dateline, resulting in a net gain of 21 hours.

The Northeast route (NE) enters the Arctic zone during hour 4 as well, and stays there for the next 5 hours. If we stop the clock when we enter the region and restart it 5 hours later upon re-entry into the sub-Arctic, you will have fast forward the clock by 9 time zones, and the net result will be a net gain of about 18 hours.

Halachik events during the flight

When one enters a new Halacha Zman, i.e. when the time of day moves from morning to afternoon, a new obligation for tefila is triggered. In this case, one must daven mincha. When day changes to night, one must daven Marriv. However, if one crosses the dateline, and enters a new day while the time of day remains the same, a strange set of circumstances has arisen. The calendar declares it to be a new day at a particular location even though one has experienced no change with regard to one’s own personal state. If one moves in a westerly direction when crossing the dateline, and the day/date jumps forward, a new obligation for Tefila may be triggered even though one did not enter a new time of day. In other words, if one davened Mincha before crossing the dateline on a Monday, and crosses the dateline whereby he now finds himself in a location that is Tuesday afternoon, one may have to daven Mincha again! On the other hand, if one flies in an easterly direction, whereby the day/date repeats itself, even as one experiences a new sunrise, the obligation to daven Shacharis may not be triggered as one has already davened Shacharis for that day. This has been dealt with at length in The Dateline in Halacha.

Furthermore, the flight path, which can take one west of the Pole in which case the dateline is crossed, or east of the Pole, in which case the dateline is not crossed, may have serious implications as to the obligations to daven.

Practical Guidance to the traveler

Because of the complexity of the subject matter, it would be very difficult to create a matrix of possibilities as to how to Halachically deal with transpolar flights. The factors to be considered are

Flight path


Time of departure

Zmanim determination based on elevation

Halachik dateline location

Halachik effects of crossing the dateline

I would suggest that unless one is quite familiar with transpolar flight, that before embarking on the trip, to email me the flight itinerary, and we might be able to work out a solution together on a case by case basis.

Case Studies

This section examines how Halacha would apply to actual flight patterns. These studies are theoretical in nature but it does give you a good idea of what goes into the decision making process.

New York to Hong Kong


Northwest Route

The flight takes off from NY at 2 AM on Monday. It is dark outside. For the first 4 hours of the flight, you flew due north. The longitude has hardly changed. However, by the end of hour 3, when local time is 5 AM, you will notice it is getting light outside. After all, Nautical Twilight at that location was at 4:41 (at sea level. At an elevation of 30,000 feet, apparent NT was much earlier).

By the end of hour 4, local time is 6 AM while sunrise is at 6:39. Time to daven Monday morning Shacharis.

But strange things happen during the next 4 hours. The flight starts veering west. By the end of hour 6 you have moved through 3 time zones. But during hour 7, you will cross the halachik dateline (145W). The end result will be that you started hour 7 at 6 AM on Monday, and by the end of hour 7 it is 1 AM (5 hours earlier on the clock), but it is now Tuesday morning (19 hours later)!

Since you are still in the polar region, even though it may be 1 AM, it is light outside.

As you continue south, you re-enter the sub-polar region during hour 10. By the end of hour 10, local time is 1 AM, but at this location, south of the Arctic Circle, the sky darkens. It is now Monday night, Tuesday 1 AM. You can daven Maariv (that is Monday night Maariv).

Mysteriously, you missed Monday mincha.

By the time you land in HK at the end of hour 15, local time will be 6 AM, sunrise will be at 7:27, and you will be able to daven Tuesday Shacharis then.

Northeast Route

Taking the same flight as above, but going Northeast, the sequence of davening is slightly different

By the end of hour 3, local time is 6AM. This is well after Alos, almost in time for sunrise. Time for Monday morning Shacharis.

By the end of hour 6. Local time is 1 PM, time for Monday Mincha. But because one is traveling in the polar zone, one passes through 7 time zones in the next hour. By the end of hour 7, it is after sunset. Nightfall will not be realized however until end of hour 9, at which time it will be 11 PM local time. Zman Maariv.

Landing is 6 hours later, where local time is 6 AM Tuesday morning, about 1 hour before sunrise.

This route allowed for all tefilos. Unlike the NW route, Mincha was not missed.



Because the sun will never rise at all during this flight, there will be no opportunity to daven Monday Shacharis. You will not experience a sunrise until you land in HK. And by that time it will be Tuesday morning.

However, there is one unnoticed halachik event. The dateline was crossed during hour 7. Sunday night (early Monday morning) became Monday night (early Tuesday morning). When this dateline was crossed, although it is dark throughout, an obligation to daven Monday night Maariv may have been triggered, and the time of Maariv will carry all the way through the night until Tuesday morning twilight at about an hour before landing.


Following this route in December, because it is dark during the whole flight, and the dateline is never crossed, it is unclear whether or one must daven the Monday night (Tuesday morning) maariv. Between hours 3 and 8, 11 time zones are crossed. One entered the polar region at 6AM during hour 4, and exits it during hour 9, where local time is 11PM Monday night. In theory, it is time for Maariv. Unlike the NW route where the dateline crossing was the trigger to obligate a new Maariv, in this case the dateline crossing was not the trigger. Re-entry into time zones where sunrise and sunset play a role seems to be the trigger.



This is the longest day of the year. By the end of hour 2 you will have reached the 63rd parallel where sunrises is at 4:05 am. Time for Shacharis. The rest of the flight is during daylight. However, local time never reaches the afternoon hours. Re-entry into the sub Arctic zone is at the end of hour 10, where local time is 1 AM. At this location on our model, the longitude is 63N, only about 3 degrees south of the Arctic Circle. Sunrise is at 2:41, sunset at 10:59.

Interestingly however, as you continue south, you will enter night AFTER you experienced an early sunrise. At the end of hour 11, where the latitude is 55N, local time will be 2 AM and sunrise will not take place until 4:21. You have an opportunity to daven Maariv.

When you land at 6 AM, the sun will have already risen and time to daven Shacharis.


By the end of hour 2, you will have crossed 1 time zone, local time will be 5AM, and sunrise at that location is at 4:05. Time for Shacharis.

As you continue fast through time zones, by the end of hour 6 you will be quite close to the North Pole. Local time at that location is 1PM. At trhe end of hour 7 local time is already 8 PM. It would seem that one should daven mincha during that hour.

By the end of hour 10, you have re-entered the sub Arctic, local time is midnight, and sunset was at 10 PM. You can daven Maariv.

With this flight as well, you will land at 6 AM local time, shortly after sunrise. Time for Shacharis.

Fast days

The interesting question of fast days comes up on 17 Tamuz. When flying from NY to HK one flies almost due north for 4 hours before reaching the Arctic Circle. Once above the Arctic Circle, it is daylight for the next 5 hours. The halachik dateline is crossed during hour 7 of the flight.

Assume that the fast is on Tuesday. If we take a Monday night 1 AM flight out of NY (that is early Tuesday morning 17 Tamuz), it will land at 5 AM Wednesday morning 18 Tamuz. The fast will begin when one sees daylight, after about hour 3. When one crosses the dateline at hour 7, it is now Wednesday, local time 11PM. The fast should theoretically end at this point. This is in fact the opinion of some. However, as mentioned above, some poskim feel that a fast cannot end midday under any circumstances in which case, one must wait until the sun sets about 3 hours later as the flight takes you below the Arctic Circle. The net difference between the two opinions is about 3 hours. The length of the fast day in this scenario will be between 4 and 7 hours.

The 10 AM flight is a completely different story. Takeoff is at 10 AM on Tuesday 17 Tamuz and lands at 2 PM on Wednesday 18 Tamuz. If one takes this flight the fast has already begun about 6 hours before takeoff. The dateline is reached about 7 hours later where local time is noon on Tuesday, but as we cross the dateline it becomes noon on Wednesday which is not a fast day. Accordingly, according to some opinions mentioned above, one may break the fast then.

However we did cite an opinion of some of the most prominent poskim who are of the opinion that a fast cannot end midday. Although the calendar day may say it is Tuesday, the 18th of Tamuz, since one began the fast at the appropriate time, one must wait about another 12 hours before reaching sunset, about 4 hours after the plane lands in Hong Kong. The fast will be a full 26 hours.

Hong Kong to New York

For this study, let us discuss a flight that leaves Hong Kong at 10 AM on Friday and lands in New York 15 hours later at 2 PM Friday (same day).

The different flight paths, for the most part have little halachik impact. The more southerly route follows a path beneath the Arctic Circle with a maximum latitude on about 60N. The northern route may go as far north as 70N. Halachik ramifications of the differences between these paths are minimal. In either case, the halachik dateline is reached at about 9 hours after takeoff.

As the plane leaves from HK at 10 AM, one should have davened Shacharis before boarding. About 2 hours later, as you fly east through advancing time zones, you reach time for mincha where local time is 1 PM.

The next halachik event, reaching nightfall or the dateline depends on the time of year. This is very significant.


The dateline is reached at the end of hour 9. Friday sunset occurs when local time is about 6 PM, five hours into the flight. So from hour 5 to hour 9 one is in a Shabbos state. During this time one must refrain from melacha. The Shabbos state ends when the dateline is reached, at about the end of hour 9. When you reach the dateline, the day is pushed back to Thursday night.


In December, the Shabbos issue is a bit longer. Sunset occurs closer to 4 PM local time, about 4 hours into the flight. The day is not pushed back to Thursday night until 9 hours into the flight. Hence, on is in the Shabbos state for about 5 hours.

However, once the dateline is crossed, during Thgursday night, what halachos may apply for the balance of the trip?

Thursday night Maariv does not have to be repeated since one already davened Thursday night Maariv in Hong Kong. One may however opt to daven Shmoneh esrei as nedava. The only obligation is to say Shma, as Shma is not day/date sensitive. The obligation is triggered by Beshochbecha Uvekumecha, when it is turns dark at night or light by day. Hence, Shma without birchos krias Shma is obligatory.

(A frequently asked question is why might one not have to daven the Friday night maariv and say Kiddush while in the Shabbos state. It is a great question, but we cannot deal with it here).

Several hours later, when one experiences a new sunrise, the sunrise is that of Friday, a second Friday sunrise; the first Friday sunrise took place while still in Hong Kong. Sunrise triggers two halachos; birchos hashachar and Shma. The other mitzvos, such as Tefila, is the subject of a machlokes mentioned above. Most poskim feel that a Shacharis Shmoneh esrei is not required, though one may always daven nedava. However birchos krias Shma as well as birchos pesukei dezimra should not be said. With regard to tefilin, it is highly recommended to put them on when saying Shma.


Depending on the route, one may or may not encounter Shabbos. If the pilot flies the more northerly route, one may not reach sunset before reaching the dateline, in which case one will cross the dateline on Friday afternoon before sunset thus moving the day back to Thursday afternoon.

Even when taking the southern route, one may reach sunset at about hour 8, in which case the traveler will be in the Shabbos state for only about an hour. (Note that visual sunset can be deceiving as at the high altitude, sunset can be off by an hour or more).

Miscellaneous Halachik Issues

Having traveled to the Far East for business, I have come across Halachik areas of concern more prevalent in The Far East, for which I would like to raise awareness.


A businessman’s hotel room is his office away from home. Many business meeting with suppliers take place in the room. The visitors are often women, or a man accompanied by a woman. Meeting in a hotel room with the door closed can raise serious issues of Yichud. The laws of Yichud are complex. Generally one or two men should not be in a closed room with one even two woman. The door must be held open in such circumstances. It is highly recommended that meetings be held in more public areas.

Cholov Yisroel

The well known and accepted heter that does not require one to limit consumption of dairy products to Cholov Yisroel is not applicable to many countries in the Far East. The heter is based on government inspections in The U.S, and penalties for non compliance. These laws do not exist in many countries outside the U.S.

Vegetarian and Buddhist Restaurants

I have met many very religious businessmen who feel that one may eat in Buddhist restaurants where animal derivatives are strictly prohibited. The problems with eating in these restaurants are numerous. The definition of what is considered animal derivative is not clear among many segments of Buddhist. Clams or clam juice for instance are commonly found in these restaurants. One may absolutely not rely on what he is told by the local mashgiach. Needless to say, all dishes cooked in these restaurants would be considered Bishul Akum.

I have seen religious Jews eat raw fish such as sashimi, arguing that since it is not cooked one may eat it. This is a very questionable practice and should certainly be avoided. There is no heter for this.

Another common area of concern is ordering a “simple” salad with no dressing. Much has been written on the subject of bugs found in salad, and whatever issues may exist in the States are of far greater concern in the Far East. One should exercise extreme caution.

Beer in Lounges or Bars

While businessmen will refrain having dinner with their business associates because of kashrus concerns, joining others for a “drink” at the hotel lounge or local bar is seen as a kosher substitute. One cannot after all snub their Chinese hosts by refusing all social invitations.

The Shulchan Aruch Y.D. 114:1 states that one is not permitted to drink beer in a place where beer is sold, i.e. in a bar or cocktail lounge. This has nothing to do with kashrus. It was a law established by Chazal to prevent fraternizing. The Rama notes that the common custom is to permit this as the original law possibly only applied to beer made of dates and not beer made of hops as we have today. Many later poskim (GRa, Chochmas Adam) rule against the Rama, and recommend in the strongest terms that drinking beer at the pub should be greatly discouraged. Furthermore, the leniency of this Rama may not apply to Sefardim. One must check with his rabbi.


Please refer to the following link from the Star-K’s Kashrus Kurrents Spring 2010 edition where the many issues that may arise when staying in a hotel for Shabbos are discussed.


A polar view of two NY-HK flights, one taking the Northwest route (yellow) which crosses the date line (red), and one taking the Northeast route (white).

A frontal view of Map 1 as seen with the Pacific Ocean at center. The NW route (yellow line) looks like it flies high above Canada, Alaska, and Siberia.

A frontal view of Map 1 as seen when with the Atlantic Ocean at center. The NE route (white line) looks like it flies high above Greenland, Sweden, Finland, and Russia.

A Flat Map view of the Northwestern route. This is the route seen on the screen on the plane. It is a flat view of Map 2.

A Flat Map view of the Northeastern route. This is the route seen on the screen on the plane. It is a flat view of Map 3.

A close-up polar view of the sixth hour of the NY-HK flight as it flies close to the North Pole. Note how the NW route dissects the Dateline while the NE route does not. Also note that during hours 7 and 8 the plane crosses through about 7 time zones.

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