Question:

Why do Some Zmanim Never Occur in Some Locations? (Developers Beware)

Answer:

While most people realize that the sun may not rise or set in the Arctic and Antarctic Circles (see the Star-K’s When Does One Pray When There Is No Day), many are not aware that some twilight dips will not occur during part of the year as far south of the Arctic Circle as London. For example around the summer solstice in London (on the zmanim map) the sun will never dip far enough below the horizon to reach Alos 16°. This happens in London from June 5^th till July 8^th. The image seen on the top right (original at timeanddate.com) shows various civil twilights centered on London on Midnight June 21^st. Look carefully to see the various bands of twilight. Gateshead will not have Alos 16° from May 16^th through July 28^th, while Anchorage, Alaska (yes there is a Frum Shul in Anchorage with an interesting davening direction issue that will require its own post) will not have Alos 16.1° from April 25^th to August 20^th. Zmanim based on sunrise such as Also 72 that is a 72 minute offset of sunrise can be calculated as long as sunrise can be calculated, something that will happen as long as you are not in the Arctic or Antarctic Circles.
For this reason, the Zmanim API will return a null when a zman will not happen. A Long.MIN_VALUE will be returned when a long is expected such as in the case of a Shaah Zmanis. While an inconvenience to developers who have to code for this, the alternative of a default date would mean that developers unaware of this would return incorrect zmanim, something far worse than a program error from a NullPointerException.
In recent weeks two publicly available programs using the Zmanim API ran into issues due to nulls returned for early alos times. Being something not anticipated by the developers, the nulls generated errors in the programs that quickly led to fixes. For this reason Yitzchok updated the Zmanim .NET project to return the nullable DateTime? instead of the regular DateTime that it had previously been returning. While the Zmanim API documentation always made the possibility of a null being returned possible, I modified the documentation to make this clear on the return value documentation for every zman. Code with the modified documentation was part of the recently released Zmanim API 1.2.1.

C#

using Zmanim.TimeZone;
using Zmanim.TzDatebase; //in Zmanim.TzDatebase.dll assembly
using Zmanim.Utilities;

namespace Zmanim.Samples.Console
{
    class Program
    {
        static void Main(string[] args)
        {
            string locationName = "Lakewood, NJ";
            double latitude = 40.09596; //Lakewood, NJ
            double longitude = -74.22213; //Lakewood, NJ
            double elevation = 0; //optional elevation
            ITimeZone timeZone = new OlsonTimeZone("America/New_York");
            GeoLocation location = new GeoLocation(locationName, latitude, longitude, elevation, timeZone);
            ComplexZmanimCalendar zc = new ComplexZmanimCalendar(location);

            System.Console.WriteLine("Today's Zmanim for " + locationName);
            System.Console.WriteLine("Sunrise: " + zc.GetSunrise()); //output sunrise
            System.Console.WriteLine("Sof Zman Shema MGA: " + zc.GetSofZmanShmaMGA()); //output Sof Zman Shema MGA
            System.Console.WriteLine("Sof Zman Shema GRA: " + zc.GetSofZmanShmaGRA()); //output Sof Zman Shema GRA
            System.Console.WriteLine("Sunset: " + zc.GetSunset()); //output sunset

            System.Console.WriteLine("Press enter to exit.");
            System.Console.ReadLine();
        }
    }
}

VB.NET

mports Zmanim.TzDatebase 'in Zmanim.TzDatebase.dll assembly
Imports Zmanim.Utilities
Imports Zmanim.TimeZone

Module Module1

    Sub Main()
        Dim locationName As String = "Lakewood, NJ"
        Dim latitude As Double = 40.09596 'Lakewood, NJ
        Dim longitude As Double = -74.22213 'Lakewood, NJ
        Dim elevation As Double = 0 'optional elevation
        Dim timeZone As ITimeZone = New OlsonTimeZone("America/New_York")
        Dim location As New GeoLocation(locationName, latitude, longitude, elevation, timeZone)
        Dim zc As New ComplexZmanimCalendar(location)

        System.Console.WriteLine("Today's Zmanim for " & locationName)
        System.Console.WriteLine("Sunrise: " & zc.GetSunrise().ToString)
        'output sunrise
        System.Console.WriteLine("Sof Zman Shema MGA: " & zc.GetSofZmanShmaMGA().ToString)
        'output Sof Zman Shema MGA
        System.Console.WriteLine("Sof Zman Shema GRA: " & zc.GetSofZmanShmaGRA().ToString)
        'output Sof Zman Shema GRA
        System.Console.WriteLine("Sunset: " & zc.GetSunset().ToString)
        'output sunset
        System.Console.WriteLine("Press enter to exit.")
        System.Console.ReadLine()

    End Sub

End Module

The current Zmanim .NET TODO list for the project includes:

• Remove dependency to Java (IKVM assemblies)
• The API should follow the .NET guidelines
• Make it Linq friendly
• Add examples how to use this project in a ASP.NET MVC site and WPF Application
• Try to get it to work on Silverlight

I Googled around, and found your project.

One of my goals with the API was to make it easy for developers to use and port. This was confirmed by Jay

I found it to be very easy to pull into my app, even on Android…no changes necessary, not even a recompile

Updated on 4/13/2010 to reflect information from Moshe explaining that this was not a port

/**
 * This program demonstrates how to calculate bearing to Yerushalayim
 * using the kosherjava.com Zmanim API. Both the great circle and
 * rhumb line method are shown
 * To compile, ensure that the Zmanim Jar is in your classpath.
 */
import net.sourceforge.zmanim.util.GeoLocation;
import java.util.TimeZone;

public class BearingToYerushalayim{
	public static void main(String [] args) {
		GeoLocation lakewood = new GeoLocation("Lakewood, NJ", 40.09596, -74.22213, 0, TimeZone.getTimeZone("America/New_York"));
		GeoLocation harHabayis = new GeoLocation("Har Habayis", 31.77805, 35.235149, 0, TimeZone.getTimeZone("Asia/Jerusalem"));

		double greatCircleInitialBearing = lakewood.getGeodesicInitialBearing(harHabayis);
		double greatCircleDistance = lakewood.getGeodesicDistance(harHabayis);

		double rhumbLineBearing = lakewood.getGeodesicInitialBearing(harHabayis);
		double rhumbLineDistance = lakewood.getRhumbLineDistance(harHabayis);

		System.out.println("Great circle initial bearing: " + greatCircleInitialBearing + " degrees ");
		System.out.println("Great circle distance: " + greatCircleDistance/1000 + " KM");

		System.out.println("Rhumb line bearing: " + rhumbLineBearing + " degrees");
		System.out.println("Rhumb line distance: " + lakewood.getRhumbLineDistance(harHabayis)/1000 + " KM");

	}
}

moshe@debian:~/Desktop$ java -jar ZmanimCLI.jar sunrise
6:10:28

moshe@debian:~/Desktop$ java -jar ZmanimCLI.jar --date 2010/08/12 tzais72
20:38:15

moshe@debian:~/Desktop$ java -jar ZmanimCLI.jar
Usage: ZmanimCLI [options] [Time]

Options:
       -d      --date <yyyy/mm/dd>             Set date. (Year first!)
       -lat    --latitude <latitude>           Set location's latitude
       -lon    --longitude <longitude>         Set location's longitude
       -e      --elevation <elevation>         Set location's
elevation; Positive only
       -tz     --timezone <timezone>           Set location's TimeZone

Help:
       -h      --help                          Show this help
       -stl    --time-list                     Show common available
times to display
       -ftl    --full-time-list                Show all available
times to display
       -tzl    --timezone-list                 Show available timezones

Example:
       ZmanimCLI --latitude 31.7780 --longitude 35.235149 --elevation
600 --timezone Israel Sunrise
       Will show the sunrise time today in Jerusalem

While your first reaction may be that it is interesting in a theoretical geeky way, but has no practical value, I will quote Moshe’s explanation as to why it is useful:

Why is this useful?
Well, first of all it was a nice experiment. But mainly, you can now use Zmanim (although externally), via any language you want, no longer being tied to Java.

Months later, Moshe actually put this to practical use in his C++ based Luach project. This Luach (similar to the known Kaluach) uses the Qt framework. utilizing libhdate for the date stuff (something not offered by the Zmanim API, and the topic of a future Zmanim API FAQ), displaying zmanim using the Zmanim API via CLI for the zmanim calculations. While you would expect such an approach to be slow, using the Luach seemed almost instantaneous. I will post more about his Luach program (recently reviewed at KosherDev.com) at some point in the future.

Question:

Where is the main method?

Answer:

This is a more technical variant of the “How do I install the Zmanim API Program?”, but coming from someone who already knows that it is a Java program that can’t be installed, but assumes that it can be run. The main method is the entry point to a Java program. Since this is a library/API and not a program, it does not have a main method. The code to generate zmanim is spelled out in the How to Use the Zmanim API page (that will hopefully be updated in the near future). Below is a full example of a very simple zmanim program that outputs sunrise, sof zman krias shema and sunset for the current day in Lakewood, NJ. Please ensure that the Zmanim jar (download) is in your classpath.

/**
 * This program is a simple demonstration of the kosherjava.com Zmanim API.
 * To compile, ensure that the Zmanim Jar is in your classpath.
 */
import net.sourceforge.zmanim.*;
import net.sourceforge.zmanim.util.*;
import java.util.TimeZone;
public class SimpleZmanim{
	public static void main(String [] args) {
		String locationName = "Lakewood, NJ";
		double latitude = 40.09596; //latitude of Lakewood, NJ
		double longitude = -74.22213; //longitude of Lakewood, NJ
		double elevation = 0; //optional elevation
		//use a Valid Olson Database timezone listed in java.util.TimeZone.getAvailableIDs()
		TimeZone timeZone = TimeZone.getTimeZone("America/New_York");
		//create the location object
		GeoLocation location = new GeoLocation(locationName, latitude, longitude, elevation, timeZone);
		//create the ZmanimCalendar
		ZmanimCalendar zc = new ZmanimCalendar(location);
		System.out.println("Today's Zmanim for " + locationName);
		System.out.println("Sunrise: " + zc.getSunrise()); //output sunrise
		System.out.println("Sof Zman Shema GRA: " + zc.getSofZmanShmaGRA()); //output Sof Zman Shema GRA
		System.out.println("Sunset: " + zc.getSunset()); //output sunset
	}
}

The following would compile and execute this code (sample from a DOS prompt in Windows).

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

C:\path\to\code>java SimpleZmanim

Today's Zmanim for Lakewood, NJ
Sunrise: Thu Nov 05 06:30:27 EST 2009
Sof Zman Shema GRA: Thu Nov 05 09:05:21 EST 2009
Sunset: Thu Nov 05 16:50:02 EST 2009

Please see the Zmanim API documentation for a more complete view of the API.