Tag: Java

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()));
	}
}

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

KosherJava Zmanim API Released Under the LGPL License

LGPL 2.1Until this point the KosherJava Zmanim API has been released under the GPL V2.0 open source license. This had the effect of forcing any application written using the library to release it’s source code under the same license. Being that the Zmanim API is a library, the LGPL is a more appropriate license. The LGPL allows developers to use the KosherJava Zmanim API, yet keep their application code closed source. Only changes to the API itself (such as ports to different languages) would have to be released as open source. I had in the past on request released the source under the LGPL (the Zmanim API .NET port has already been released under the LGPL with my permission), and with the recent 3/27/2011 SVN checkin I formally changed the Java Zmanim API license to the LGPL 2.1 (not the newer LGPL 3.0). The next 1.3.0 release will be the first formal release under the LGPL. In one case the change to the license required permission from developer who wrote code used by the Zmanim API, and this was done.

Calculating Erev Pesach Zmanim

MatzosThe Zmanim API did not have dedicated zmanim to claculate the Erev Pesach zmanim of sof zman achilas chametz (the latest time one can eat chametz), and sof zman biur chametz (the latest time to burn chametz) till the April 14 check in to the KosherJava Zmanim Project GitHub repository. The latest time for eating chametz is at the end of the 4th hour of the day. This corresponds to sof zman tfila. The API has about 12 of those, so that does not require any special programming, but to help developers who are unaware of how they work I created 3 wrapper getSofZmanAchilasChametz methods (getSofZmanAchilasChametzGRA(), getSofZmanAchilasChametzMGA72Minutes() and getSofZmanAchilasChametzMGA​16Point1Degrees()) calling the 3 most commonly used getSofZmanTfila methods (getSofZmanTfilaGRA(), getSofZmanTfilaMGA72Minutes() and getSofZmanTfilaMGA​16Point1Degrees()). For example here is the exact code used in getSofZmanAchilasChametzGRA()

public Date getSofZmanAchilasChametzGRA() {
	return getSofZmanTfilaGRA();
}

The API itself is very flexible, and as long as you know the calculation of the zman, you can easily calculate it. For example, to calculate sof zman biur chametz according to the GR"A, the time would be 5 shaos zmaniyos after sunrise. Using the Zmanim API this would be coded as:

Date SofZmanBiurChametzGra = getTimeOffset(getSeaLevelSunrise(), getShaahZmanisGra() * 5);

The exact code used in the API is:

public Date getSofZmanBiurChametzGRA() {
	return getTimeOffset(getSeaLevelSunrise(), getShaahZmanisGra() * 5);
}

Developers who want to use the current API to generate these zmanim can use the following sample as a guide.

String locationName = "Lakewood, NJ";
double latitude = 40.09596; //Lakewood, NJ
double longitude = -74.22213; //Lakewood, NJ
double elevation = 0; //optional elevation
TimeZone timeZone = TimeZone.getTimeZone("America/New_York");
GeoLocation location = new GeoLocation(locationName, latitude, longitude, elevation, timeZone);
ComplexZmanimCalendar czc = new ComplexZmanimCalendar(location);
czc.getCalendar().set(Calendar.YEAR, 2011);
czc.getCalendar().set(Calendar.MONTH, Calendar.APRIL);
czc.getCalendar().set(Calendar.DAY_OF_MONTH, 18);
Date graAchilas = czc.getSofZmanTfilaGRA();
Date graBiur = czc.getTimeOffset(czc.getSeaLevelSunrise(), czc.getShaahZmanisGra() * 5);
Date mga72Achilas = czc.getSofZmanTfilaMGA72Minutes();
Date mga72Biur = czc.getTimeOffset(czc.getAlos72(), czc.getShaahZmanisMGA() * 5);
Date mga16Achilas = czc.getSofZmanTfilaMGA16Point1Degrees();
Date mga16Biur = czc.getTimeOffset(czc.getAlos16Point1Degrees(), czc.getShaahZmanis16Point1Degrees() * 5);
System.out.println("Erev Pesach Zmanim for " + locationName);
System.out.println("Sof Zman Achilas Chametz GRA: " + graAchilas);
System.out.println("Sof Zman Biur Chametz GRA: : " + graBiur);
System.out.println("Sof Zman Achilas Chametz MGA 72 Minutes: " + mga72Achilas);
System.out.println("Sof Zman Biur Chametz MGA 72 Minutes: " + mga72Biur);
System.out.println("Sof Zman Achilas Chametz MGA 16.1 Deg: " + mga16Achilas);
System.out.println("Sof Zman Biur Chametz MGA 16.1 Deg: " + mga16Biur);

this would output

C:\path\to\code>javac ErevPesachZmanim.java

C:\path\to\code>java ErevPesachZmanim

Erev Pesach Zmanim for Lakewood, NJ
Sof Zman Achilas Chametz GRA: Mon Apr 18 10:42:42 EDT 2011
Sof Zman Biur Chametz GRA: : Mon Apr 18 11:49:39 EDT 2011
Sof Zman Achilas Chametz MGA 72 Minutes: Mon Apr 18 10:18:42 EDT 2011
Sof Zman Biur Chametz MGA 72 Minutes: Mon Apr 18 11:37:39 EDT 2011
Sof Zman Achilas Chametz MGA 16.1 Deg: Mon Apr 18 10:13:56 EDT 2011
Sof Zman Biur Chametz MGA 16.1 Deg: Mon Apr 18 11:35:18 EDT 2011