FAQ: How do I Calculate the Jewish/Hebrew Date for …?

This FAQ is now obsolete. Jewish Calendar Calculations are now supported. See the Zmanim API 1.3.0 Release announcement

Question:

How do I get the Jewish Date for … using the Zmanim API?

Answer:

The current version of the Zanim API does not support Jewish calendrical calculations. Zmanim are almost exclusively based on the solar calendar, so for example, the sunrise on February 8th this year in Montreal (or any other date and location), will be almost the same every year. for this reason there was little point (as far as zmanim) to support Jewish date calculations in the API. One of the only zmanim to rely on a Jewish date is the sof zman kidush levanah calculation, though there are some opinions that it is purely molad based, and this can be calculated without a Jewish calendar component to the API. This zman is obviously not currently implemented in the Zmanim API. I am currently working on adding Jewish date support to the API. The code is based off Avrom Finkelstein‘s no longer active HebrewDate project. I refactored a lot of the code and fixed a number of bugs. Anyone interested in alpha testing this code can download the latest Zmanim SVN code.
I mentioned that it “will be almost the same every year” and this is due the approximate 1/4 day drift between the 356 day calendar year and the approximately 365.25 days actually present in the astronomical year, a discrepancy corrected every leap year. A future FAQ (probably a few of them) may delve specifically into this drift as well as general zmanim accuracy issues in detail.
If you are simply looking to convert a Hebrew date to Gregorian or Gregorian to Hebrew online without the API, try the JewishGen calendar conversion tools.

Zmanim API 1.2.1 Released

The Zmanim API 1.2.1 was released today. Changed in this release were the addition of a few very early Tzais zmanim, and the removal of references to the GregorianCalendar in favor of the base Calendar class to ease Noah Blumenthal’s use of the Zmanim API in a zmanim application for the BlackBerry. This change has no impact on functionality as tested using Yitzchok’s new JUnit tests. Additionally, the JavaDoc Zmanim API documentation was modified to clearly indicate that zmanim can return nulls. A followup post will have details on this.
The main download is the Zmanim 1.2.1 release zip file that includes source files and JavaDoc documentation. Also available for download (included in the above zip file) is the main zmanim-1.2.1.jar and the zmanimAstronomical-1.2.1.jar that only includes the AstronomicalCalendar. The removal of the GregorianCalendar was in this class. Additional detail on the downloads can be seen on the Zmanim Download page

ZmanimPlasma (Linux) Released

Linux on Wood Background
Moshe Wagner recently released ZmanimPlasma for the Linux platform. This KDE Plasma desktop widget displays the Hebrew date and zmanim on a Linux desktop. The zmanim calculations use Moshe’s C++ port Zmanim CLI wrapper that enables a C++ program to call the Java Zmanim API. There are no current plans to make this widget available on any other platform. It can be downloaded from the Luach project download page. Moshe has in the past used the Zmanim API for use in Linux and some cross platform projects. These include the above mentioned Zmanim CLI, and Zmanim GUI that uses the ZmanimCLI.

Updated on 4/13/2010 ג׳ אייר תשע״ג to reflect information from Moshe explaining that this was not a port.

Zmanim API 1.2 Released

The Zmanim API 1.2 was released today. The only change in this release is the removal of elevation as a factor in the calculation of all zmanim besides sunrise and sunset. Updated JavaDocs now reflect these changes. Please see the Elevation Now Only Impacts Sunrise and Sunset Calculations in the Zmanim API post for additional information.

I would like to thank the various people who contacted me on the subject.

The main download is the Zmanim 1.2 release zip file that includes source files and JavaDoc documentation. Also available for download (included in the above zip file) is the main zmanim-1.2.jar. The zmanimAstronomical-1.1.jar that only includes the AstronomicalCalendar was not impacted by this change, but the version has been updated to zmanimAstronomical-1.2.jar for consistency. Additional detail on the downloads can be seen on the Zmanim Download page

Zmanim API 1.1 Released

The Zmanim API 1.1 was released early this morning. Information about what changed in this release can be seen in previous posts about various beta and patch releases. A last-minute change involved the removal of the misheyakir calculations commonly used by the Syrian community. The removal was due to the various different minhagim used, and Chacham Yosef Harari-Raful not endorsing any specific one, nor does he include any in his calendar. The API is flexible enough to be used for any calculation wanted by the various Syrian shuls even without “native” support for a built in “Ateret Torah” misheyakir. Some missing JavaDocs were also added.

I would like to again thank Rabbi Rachamim Ashkenazi the publisher of a zmanim calendar for the Syrian Community, and Victor Grazi for his input, testing and technical expertise used for adding the new “Ateret Torah” zmanim.

The main download is the Zmanim 1.1 release zip file that includes source files and JavaDoc documentation. Also available for download (included in the above zip file) is the main zmanim-1.1.jar and the new zmanimAstronomical-1.1.jar that only includes the AstronomicalCalendar and supporting classes. Additional detail on the downloads can be seen on the Zmanim Download page.