Sunday, March 29, 2009

Birkat HaChamah Online Book

I've been writing a (short) book on the math behind Birkat HaChamah for the last year or so, and I have decided to start to make it public online with Google's new web publishing app.  I have 8 chapters, an appendix, and I've translated Pirkei D'Rebbi Eliezer chapters 6 and 7.  Please leave comments on this post if you have any.

Here's the link.
Update:  All parts of this book have been put online.


  1. The problem with all of this is that the math is outdated. The accepted astronomical value for a solar year is 365 days 5 hours 48 minutes and 46 seconds and not the 365 days and 6 hours. In the 5769 hears from creation the most accuate year ever to say this brachah from an astronomical point of view was 4712. This year is quite far off.

  2. Jonathan, you didn't read the other articles on this blog regarding this topic. This is addressed.

  3. חזק וברוך

    In Appendix 5, you ask: Why is Birkat HaChamah referred to as Kiddush HaChamah?

    Many Ashkenazic sefarim refer to it as Kiddush Hahama just as they refer to Birkat Halevana as Kiddush Levana. I can find other references if you're interested.

    Your second question - I wish I knew the answer to.

    Your third question - I don't quite understand. All he said is that Erev Pesah in Mitzrayim was on a Wednesday.

    Your other questions are valid, with the possible exception of #2 if you can say that the Purim story didn't happen quite at that date, depending on who Ahashveirosh really was.

  4. It is well known that Erev Pesach was Yom Revi'i in the year of the Exodus. But of course that is not related to the Tekufah, or davka the 28 year cycle.

    Regarding the 3rd question, I think you're right. I'll remove it.

    I don't get what you're saying about Purim. Hachrazat Koresh is around 3390, and the 2nd year of Daryavesh is 3408 or 3409. Birkat HaChamah is before and after this period.

  5. The dating of Purim is not universally accepted as being those dates, so maybe it comes out to be a date that fits in better. Just a possibility.

  6. Yaak,

    When we discuss things like Birkat HaChamah, we use traditional dating. What traditional source would say that Purim was after Daryavesh or before Koresh?