FAQ: Calculating the Baal Hatanya’s Shkiah

Baal Hatanya Zmanim

Please see the more recent and updated article Baal Hatanya’s Zmanim Added to KosherJava Zmanim Library for more current information.

Question:

How do I calculate the בעל התניא Baal Hatanya’s Zman for Shkiah as 4 minutes after sunset using the KosherJava Zmanim API?

Answer:

I was recently asked how to use the Zmanim API to calculate the Baal Hatanya’s opinion is that shkiah (halachic sunset) is 4 minutes after civil sunset. The assumption that the Baal Hatanya’s shkiah is a fixed 4 minutes after sunset is not that simple and will require a separate post to clarify. This zman should not be used lehalacha without consulting a rov. This post shows how to us the API assuming that it is a fixed 4 minutes after sunset. The technique to calculate this with the API is identical to the way getTzais72() would be calculated. The source of that method is

public Date getTzais72() {
return getTimeOffset(getSeaLevelSunset(), 72 * MINUTE_MILLIS);
}

The getTimeOffset(Date time, double offset) method in the base class AstronomicalCalendar is very simple:

public Date getTimeOffset(Date time, long offset) {
if (time == null || offset == Long.MIN_VALUE) {
return null;
}
return new Date(time.getTime() + offset);
}

The getTimeOffset method simply adds the number of milliseconds of the offset to the raw time of the zman and returns it as a date. While using the API itself is not needed for such a simple calculation, here is how it would be used:

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);
Date baalHatanyaShkiah = zc.getTimeOffset(zc.getSeaLevelSunset(), 4 * 60000);
System.out.println("Baal Hatanya Shkiah: " + baalHatanyaShkiah);

Adding it to the API itself would be even simpler:

public Date getShkiahBaalHatanya() {
return getTimeOffset(getSeaLevelSunset(), 4 * MINUTE_MILLIS);
}

At some point in the future I may (doubtful) add this time to the API itself. The zman is not commonly used, and the Chabad calendars that I have seen all use regular sunset.

Update on ‍‍July 5, 2015 – י״ח תמוז תשע״ה: This article was updated to clarify that the Baal Hatanya’s opinion may not be a fixed 4 minutes, but that the post was showing how to use the API to calculate it based on the questioner’s assumption that it was a 4 minute zman.
Update on Dec 14, 2018 – ו׳ טבת תשע״ט: This article was superseded with the more recent and corrected article Baal Hatanya’s Zmanim Added to KosherJava Zmanim Library.

Zmanim API 1.3.0 Released

The Zmanim API version 1.3.0 was released on March 4th, 2013 כ״א אדר תשע״ג. Various changes in the new release VS the previous version 1.2.1 that was released in May 2010 can be seen below. This release includes beta support for Jewish Calendar calculations as well as a number of updated zmanim and refactored code. The Jewish Calendar support in the Zmanim API is based on Avrom Finkelstien’s HebrewDate project released in 2002. Unlike the Zmanim code, the Jewish calendar interfaces may change significantly in the future (see Jay Gindin’s various changes that may make it into this API) and should therefore be considered beta.

Changes in the Zmanim API 1.3.0 release

Changes since March 23, 2011 have been in SVN and detailed changes can be seen there.

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.

Zmanim API Ported to .NET (C#)

Yitzchok ported the Zmanim API from Java to a .NET API using C#. The Zmanim .NET project was released under the LGPL 2.1. This is a change from the GPL used by the Java API, something that may change shortly. Also part of the project was the creation of a C# version of the Zmanim CLI, matching Moshe Wagner’s Java Zmanim CLI. When developing the project, Yitzchok created the ZmanimTest JUnit test case class to confirm that the C# port output matched the Java API. I will likely add this to the core Zmanim API in the near future. The port currently relies on IKVM assemblies as can be seen in the Java references in the code sample below, mostly because of the lack of a native .NET equivalent of the Java TimeZone class. Yitzchok also created some examples of the use of the Zmanim .NET API that will be of help to developers. Below are two of the simpler examples in C# and VB.NET demonstrating a very simple use of the API to output zmanim from the console.

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);
            //optionally set it to a specific date with a year, month and day
            //ComplexZmanimCalendar zc = new ComplexZmanimCalendar(new DateTime(1969, 2, 8), 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)
        'optionally set it to a specific date with a year, month and day
        'Dim zc As New ComplexZmanimCalendar(New DateTime(1969, 2, 8), 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

Android Zmanim Using the KosherJava Zmanim API

Android Logo
Android ZmanimThere are various software projects using the KosherJava Zmanim API. One of the active ones is Jay Gindin’s open source Android Zmanim app for the Android platform. Activity in the project is constant. The upcoming version allows the selection of a specific calculation for zmanim you want such as the zman Talis/Tefilin pictured here. There are plans to add direction to Yerushalayim functionality using the Zmanim API. (For more information on calculating bearing using the API, see Calculating the Bearing/Direction to Har Habayis Using the Zmanim API article.) A large part of Jay’s motivations for developing the code was lezecher nishmas his nephew Shemuel Reuven ben Yehudit Rachel who, lost his battle with cancer on October 21, 2009. The one very minor issue Jay had with the API (and documentation) was the Ashkenazi spelling of the zmanim names, something that as an Ashekenazi I do not plan to change :), but as you can see his Android Zmanim front end used Sephardi labeling. Asked how he found the project, he answered with the typical answer to this question

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