CH”M is an abbreviation for Chol Ha-Mo’ed. Chol Ha-Mo’ed are the intermediate days of Passover and Sukkot, when work is permitted.
Why are fixed fast days sometimes observed on a different day?
For example, Tzom Tammuz is always on the 17th of Tammuz, but in the year 5772 (2012 C.E.) it is on the 18th of Tammuz. The answer has to do with Shabbat:
“The Hebrew year contains several fast days that, though specified by particular Hebrew calendar dates, are shifted when those days occur on Saturday. The fast days are Tzom Gedaliah (Tishri 3), Tzom Tevet (Tevet 10), and Tishah be-Av (Av 9). When Purim is on Sunday, Ta’anit Esther occurs on the preceding Thursday… Each of the other fast days, as well as Shushan Purim (the day after Purim, celebrated in Jerusalem), is postponed to the following day (Sunday) when it occurs on Saturday.”
Reference: Calendrical Calculations, Edward M. Reingold, Nachum Dershowitz, Cambridge University Press, 2001, page 109.
Displaying Shabbat candle-lighting times on your website
Hebcal.com’s Add Shabbat Times to your Website tool lets you create custom HTML tags to which display weekly candle-lighting times directly on your web page. The result looks something like this:
Shabbat times for Chicago, IL
Candle lighting: 4:08pm on Friday, 02 January 2004
This week’s Torah portion is Parashat Vayigash
Havdalah (72 min): 5:39pm on Saturday, 03 January 2004
1-Click Shabbat Copyright © 2004 Michael J. Radwin. All rights reserved.
Customizing Yahrzeit, Birthday and Anniversary Calendar for your website
You may use these HTML tags to insert a small form directly on your web page, with a reverse link back to your site:
Make sure you replace both the ref_url and ref_text value fields with with your own synagogue’s.
I’m a programmer. Can I see the source code?
Yes. The code is freely available under the terms of The BSD License.
Download from https://github.com/hebcal .
Hebcal.com runs on Node.js on Ubuntu Linux. The code is written in JavaScript (ES6 / ECMAScript 2015).