The Halachic Date Line Map


The International Date Line is an internationally agreed upon, arbitrarily selected, line that demarcates one calendar day from the next. This line is about 180° from Greenwich and was selected since it is opposite Greenwich and mostly runs through uninhabited areas. The line (see the gray line in the map above) meanders around national borders and island groups. The halachic date line (קו התאריך) is a complex subject with various opinions. See Rabbi Dovid Heber’s excellent article A Traveler’s Guide to the International Date Line in the Star-K Kashrus Kurrents for additional information. This line changes from time to time, as countries decide to change from one side of the date line to the other. The most recent change was when Samoa shifted to the west of the line at the end of 2011. Discussing the Samoa change in a December 29th, 2011 Yeshiva World article How to Keep This Shabbos in Samoa?, Rabbi Dovid Heber stated that

According to almost all opinions, the Halachic Date Line is not determined by what the locals call “Saturday” and therefore, the fact that Samoa changes the date line does not change when we keep Shabbos.

As far as I know, until this point, there has not been a very exact map allowing one to determine with clarity the exact parts of the world affected by the Halachic Date Line. As an example, see Rabbi Yisroel Taplin’s sefer Taarich Yisrael תאריך ישראל for a discussion about possibly not visiting the Philippines due to questions about the exact location of the date line. With the introduction of the Halachic Date Line Map such ambiguities can be laid to rest since users can zoom in to find the exact locations of various opinions on the map (see the map partially zoomed in to the Philippines for example).

Location of the Halachic Date Line

There are various opinions about the location of the halachic date line. The three main opinions of the location of the Halachic Date Line are:

  1. The חזון איש Chazon Ish quoting the כוזרי Kuzari and the בעל המאור Baal Hamaor who state that the date line is 90° east of the Har Habayis.
  2. Rabbi Yechiel Michel Tucazinsky (author of the Gesher Hachaim) who wrote the היומם בכדור הארץ Hayomam Bekadur Haaretz stating his opinion that the date line is 180° east (or west) of Har Habayis. Among those agreeing with this opinion is Rabbi Elyashiv. Since this line is exactly halfway around the world from Yerushalayim, a person on different sides of this line will face different directions when davening (using the rhumb line method). A person located west of the line will daven westward, and a person east of the line will daven eastwards. See the Bearing to Yerushalayim Map for a location along this line (the green line). Click on the blue pushpin in the map (below the green line) for additional information on the antipodal point of the Har Habayis.
  3. Rabbi Menachem Mendel Kasher in his קו התאריך הישראלי Kav Hattarich Hayisraeli is of the opinion that the International Date Line is used. Among those agreeing with this opinion was Rabbi Isser Zalman Meltzer.

The locations of the three lines are mostly over the Pacific Ocean, but in some places the lines intersect dry land. Examples of this are Russia, China, Korea, The Philippines, Indonesia, East Timor and Australia that are split by the Kuzary and Baal Hamaor’s line (see the map above). The Chazon Ish brings the opinion of the יצחק הישראלי Yitzchak Hayisraeli (a disciple of the רא״ש Rosh) in the יסוד עולם Yesod Olam 2:17 and 4:7–8, that when the line intersects dry land, the line is extended eastward (or on occasion westward according to the 180° opinion). This extension is referred to as גרירה / graira, where the land to the west “drags” the land it is attached to, to within the line. In the map, both the 90° (Chazon Ish) and 180° (Rabbi Tucazinsky) lines are measured from Har Habayis. Specifically, the measurements in the map are from the center of the Dome of the Rock. This is the location of the Kodesh Kodashim according to the רדב״ז Radvaz. According to the רד”ק Radak the center of the Dome of the Rock is the location of the mizbeach, and the Kodesh Kodashim is 101 amos (about 54 meters / 180 feet) west of this point. According to the Radak the International Date Line would be 101 amos west of the lines in the map.

How the Map Works

The Halachic Date Line Map works like any other Google Map. You can zoom into any area to see a close-up. Clicking on the lines and shaded in graira areas will provide some details about it. The map will show a very clear and exact position of the Halachic Date Line according to different halachic opinions.

Interesting points on the map

  • Tahania Atoll, a small atoll in French Polynesia that is intersected by Rabbi Tucazinsky’s line. To the south of this point is the island of Rapa Iti. There is an interesting Halachic phenomenon at this location with Kiddush Levana in December 2027. See Rabbi Heber’s Sefer Shaarei Zemanim שערי זמנים. Rabbi Heber graciously allowed me to post סימן ד׳ קונטרס זמן קידוש לבנה of the Shaarei Zemanim here. The discussion of Kiddush Levana on Rapa Iti appears on page 14 of the pdf which is page 32 in the sefer.
  • The Wrangell Mountain Homestead in Alaska, along the Edgerton Highway between Kenny Lake, and Chitina seems to be the only inhabited place that is that is intersected by Rabbi Tucazinsky’s line. The line cuts through what seems to be a barn. Thank you Rabbi Heber for this interesting observation.
  • The camping grounds and recreational area of the Childs Glacier Recreation Area in Alaska touches the line. The nearby Miles Glacier Bridge (the Million Dollar Bridge), has a clear view of the line to the west. Farther north, the Red Eagle Lodge in Gakona, Alaska is probably the closest lodging that you can find to the line, with a 3-mile westward hike (or drive along Tok Highway) to the line.
  • Ikema Island is intersected by the Baal Hamaor’s line. According to the Chazon Ish graira covers the entire Ikema Island but would not (according to Rabbi Dovid Heber of the Star-K) extend over the bridge to Miyakojima Island.
  • The line of the Baal Hamaor runs through Changchun, China a city of 7 million. According to the Chazon Ish, graira would mean the line does not split the city.
  • Are islands on Lake Argyle, that are 100 miles inland but with a river leading to the ocean included in graira using the Chazon Ish’s line? According to Rabbi Heber the river would “not ruin graira“, and such islands would be included. Would you say the same thing for French and Phillip Islands near Melbourne, Australia? Rabbi Heber is of the opinion that one should be machmir on these islands.
  • Clarity about exactly what parts of the Philippines are on the other side of the date line. Some say it is better not to travel to the Philippines due to questions of the placement of the Baal Hamaor/Chazon Ish line, but the date line map clarifies any ambiguities about this part of the world.

Additional Reading

I would like to thank Rabbi Dovid Heber for the input and assistance in preparing this post.

KosherJava Zmanim API Powering Many Mobile Apps

Mobile apps using Kosher Java Zmanim APIIn the past I posted about Android Zmanim, Jay Gindin’s open source Android zmanim project that uses the KosherJava Zmanim API. The fact that Android development uses Java natively means that it is very simple for Android developers to include zmanim in their apps. Since that time there have been a number of other applications (including iPhone apps) using the code. Moshe’s KosherCocoa Obj-C port of the KosherJava Zmanim API will probably result in additional iPhone apps that use the API. Yitzchok’s older Zmanim .NET port of the KosherJava Zmanim API also opened the door for Windows Phone zmanim applications as well (Ari Polski’s Zmaim app already uses it, and there are others in the works). I may post additional details about some of them in the future, including an updated post about Jay’s latest Android Zmanim release. I am aware of the following mobile applications that use the KosherJava Zmanim API.

There are also a few secular apps that are non-zmanim specific that use the API for sunrise and sunset calculations. One that I know of is Jeffrey Blattman’s Dawn to Dusk Widget, and I know that there are some photography apps that use it for sunrise/set calculations as well. There are likely more that I have missed, and a few that are in active development but unreleased. If you are aware of any missed apps, please let me know.

FAQ: Outputting Zmanim for A Different Time Zone With the Zmanim API

KosherJava Zmanim API FAQ

Question:

Why does the output of zmanim for a different time zone appear incorrect?

Answer:

One of the common issues encountered by developers using the API is that zmanim generated for a different time zone than the user’s time zone may return output that appears incorrect. For example a user in Lakewood, NJ trying to calculate sunrise for Yerushalayim may attempt to use the following code:

String locationName = "Jerusalem";
double latitude = 31.778; // Har habayis
double longitude = 35.2354;// Har Habayis
double elevation = 0;
TimeZone timeZone = TimeZone.getTimeZone("Asia/Jerusalem");
GeoLocation location = new GeoLocation(locationName, latitude, longitude, elevation, timeZone);
ZmanimCalendar zc = new ZmanimCalendar(location);
zc.getCalendar().set(2011, Calendar.FEBRUARY, 8);
System.out.println("Sunrise: " + zc.getSunrise());
System.out.println("Sunset: " + zc.getSunset());

While you would expect a sunrise of 6:27:41 AM and sunset of 5:19:19 PM, running this code on a computer anywhere in the Eastern Standard time zone would generate the following time that appears to be 7 hours early:

Sunrise: Mon Feb 07 23:27:41 EST 2011
Sunset: Tue Feb 08 10:19:19 EST 2011

The issue is simple, and the sunrise and sunset returned above are actually accurate. Zmanim are returned by the Zmanim API as a Java Date object that represents a moment in time (stored internally by Java as Unix Time – the number of milliseconds since the January 1, 1970 GMT). Sunrise in Yerushalayim on February 8th actually happens at 11:27:41 PM on February 7th EST. Java is simply outputting the Date as a String formatted to the users default time zone (EST in this example). The user probably intends to output the time in IST – Israel Standard Time (“Asia/Jerusalem” in the Olson database). To do this you have to output the zmanim using a formatter set to use the “Asia/Jerusalem” time zone.

DateFormat zmanimFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy");
zmanimFormat.setTimeZone(location.getTimeZone());

System.out.println("sunrise: " + zmanimFormat.format(zc.getSunrise()));
System.out.println("sunset:" + zmanimFormat.format(zc.getSunset()));

will output the expected

sunrise: Tue Feb 08 06:27:41 IST 2011
sunset:Tue Feb 08 17:19:19 IST 2011

Below is the full code example. 

import com.kosherjava.zmanim.*;
import com.kosherjava.zmanim.util.*;
import java.util.TimeZone;
public class FormatZmanim{
	public static void main(String [] args) {
		String locationName = "Jerusalem";
		double latitude = 31.778; //latitude of Har habayis
		double longitude = 35.2354; //longitude of Har Habayis
		double elevation = 0; //optional elevation
		//use a Valid Olson Database timezone listed in java.util.TimeZone.getAvailableIDs()
		TimeZone timeZone = TimeZone.getTimeZone("Asia/Jerusalem");
		//create the location object
		GeoLocation location = new GeoLocation(locationName, latitude, longitude, elevation, timeZone);
		ZmanimCalendar zc = new ZmanimCalendar(location); //create the ZmanimCalendar
		zc.getCalendar().set(2011, Calendar.FEBRUARY, 8); //set the date
		DateFormat zmanimFormat = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy"); //Create the formatter
		zmanimFormat.setTimeZone(location.getTimeZone()); //set the formatter's time zone
		System.out.println("sunrise: " + zmanimFormat.format(zc.getSunrise()));
		System.out.println("sunset:" + zmanimFormat.format(zc.getSunset()));
	}
}

Bearing to Yerushalayim and Zmanim Map 3.0

Vintage Map with CompassThe Bearing to Yerushalayim and Zmanim Map was recently updated to version 3.0. This new release adds a number of new features to the Zmanim Map version 2.0 update released in March 2010. The main change was updating the Google Map API version from the deprecated v2 to v3. This change increases performance and adds much better support for mobile browsers. The upgrade also means that a Google Maps API key is no longer required. This makes it easy to drop it into any site without any configuration (contact me for details). Zmanim tab v3The technical notes on the original Technical Information about the Bearing to Yerushalayim Map post are still relevant, with very little having changed since the initial implementation.

The following is a partial list of the new features:

  • A number of additional zmanim in the More Zmanim tab, including tchilas and sof zman kiddush levana (if they occur on that day)
  • A link to download a 12 month Zmanim calendar directly from the map (using the same spreadsheet used in the Zmanim Calendar Generator). Clicking on the link from the Zmanim tab will generate a calendar with most typically used zmanim, while clicking on the link in the More Zmanim tab will download the full set of zmanim. These are available as the Calendar Type option in the Zmanim Calendar Generator
  • Increased use of jQuery and jQuery UI for formatting the zmanim tables to better match the site look & feel
  • Refactoring to make the code more robust and slightly more maintainable
  • Timezones for all of Israel now display the timezone of Asia/Jerusalem as opposed to the Asia/Gaza returned for parts of Israel by the GeoNames TimeZone web service

From a technical perspective there were a number of changes required due to updating the Google Maps API from v2 to v3. These include:

  • v3 no longer supports tabbed info windows, so the tabs are now implemented using jQuery UI
  • Renaming of a number of classes and functions such as GLatLng to LatLng
  • A number of functions that were part of API v2 were removed in v3. One example is the removal of radians in the LatLng that had been available and was replaced by the google.maps.LatLng class. These missing functions required for the direction to Yerushalayim calculations are now supported in the Zmanim Map using prototypes

Zmanim API Ported to Cocoa / Objective-C

Moshe Berman completed the 2.0 release of his port of the KosherJava Zmanim API from Java to a Cocoa API using Objective-C. You can see the work in the KosherCocoa project page. The original work on the port dates back to Moshe’s iPhone Ultimate Omer 2 (iTunes link) app. In that app, he ported the minimum amount of code needed to calculate sunset in order to roll the day of the Omer after sunset. With Moshe’s latest check-in at github, he provided a port of a good portion of the API sticking to the basic design of the KosherJava API. The complexZmanimCalendar still remains to be ported, but the majority of zmanim in common use are in the ported ZmanimCalendar. Moshe’s blog post Introducing KosherCocoa 2.0 has additional details. Additional developer notes can be seen in the KosherCocoa wiki page. This port will be a boon to iOS developers who now have a simple way to include zmanim in their iPhone and iPad apps.
Here is some sample code that outputs zmanim to the console.

Zmanim.m

#import <Foundation/Foundation.h>
#import "ZmanimCalendar.h"

int main (int argc, const char * argv[]){

    NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];

    //  Set up the location
    NSString *locationName = @"Lakewood, NJ";
    double latitude = 40.096; //Lakewood, NJ
    double longitude = -74.222; //Lakewood, NJ
    NSTimeZone *timeZone = [NSTimeZone timeZoneForSecondsFromGMT:-18000];

    //  Initialize the Zmanim Calendar
    GeoLocation *geoLocation = [[GeoLocation alloc] initWithName:locationName andLatitude:latitude andLongitude:longitude andTimeZone:timeZone];
    ZmanimCalendar *zmanimCalendar = [[ZmanimCalendar alloc] initWithLocation:geoLocation];

    //  Create a Formatter for the date information
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setTimeZone:timeZone];
    [formatter setDateStyle:NSDateFormatterNoStyle];
    [formatter setTimeStyle:NSDateFormatterMediumStyle];

    NSDate *sunrise = [zmanimCalendar sunrise];
    NSDate *sofZmanShmaMGA = [zmanimCalendar sofZmanShmaMogenAvraham];
    NSDate *sofZmanShmaGRA = [zmanimCalendar sofZmanShmaGra];
    NSDate *sunset = [zmanimCalendar sunset];

    NSLog(@"Today's Zmanim for %@",  [geoLocation locationName]);
    NSLog(@"Sunrise: %@",  [formatter stringFromDate:sunrise]);
    NSLog(@"Sof Zman Shema MGA: %@",  [formatter stringFromDate:sofZmanShmaMGA]);
    NSLog(@"Sof Zman Shema GRA: %@",  [formatter stringFromDate:sofZmanShmaGRA]);
    NSLog(@"Sunset: %@",  [formatter stringFromDate:sunset]);

    [pool drain];
    return 0;
}

This would output (on February 8th):

Today's Zmanim for Lakewood, NJ
Sunrise: 6:58:43 AM
Sof Zman Shema MGA: 8:59:04 AM
Sof Zman Shema GRA: 9:35:04 AM
Sunset: 5:24:09 PM