While the molad is announced in terms of Jerusalem Solar Time, the tables below are shown in terms of Israeli clock time, based of the time zone (UTC +2). This allows the announced molad to be compared to the actual astronomical conjunction. The announced molad is based on the average calculated lunar cycle.
For the actual conjunction, sunset, and moonset times, I used the time charts at Time and Date along with a guess at visibility based on .6 of the time between sunset and moonset.
I assumed the Sanhedrin magically came into existence in time to declare Cheshvan because I did not want to deal with Rosh Hashannah of this year.
I also took the calculated Molad (Solar Time in Yerushalayim) and converted it to the Israeli Time Zone (UTC + 2) Clock Time as explained by Torah Tidbits in Yerushalayim. For example, the 5770 table gives the time as the Rambam declares it, as we currently announce it, and accordint to Israeli Clock Time. Thus, the time being shown is clock time rather than the actual announced time. This difference is based on the fact that noon in Solar Time (as used in the announced molad) is approximately 11:40 AM by the clock.
The point is to show what the effects would be with the various possibilities as the year progresses. I left out Rosh Hashanna because it seems that when you get a "two day" situation, Rosh Hashanna becomes Tishrei 1 and 2 rather than Elul 30 and Tishrei 1. The reason being that the entire idea of two days is based on the waiting for the declaration and the way korbanos are handled. Since Rosh Hashanna starts as soon as the declaration is made and everywhere in the country treats it as two days mishum safek, it is possible that the way we handle the same situation with every other month would be different. In any case, the entire set of comments was to show how the differences would propagate through the year.
Calculated Molad chart for the year 5770
| Month | Date | Israel Time | Rosh Chodesh |
| Cheshvan | Sunday, October 18, 2009 | 11:10 PM IST | Sun/Mon Oct 18/19 |
Kislev | Tuesday, November 17, 2009 | 11:54 AM IST | Tue/Wed Nov 17/18 |
Teves | Thursday, December 17, 2009 | 12:39 AM IST | Fri, Dec 18 |
Shvat | Friday, January 15, 2010 | 1:23 PM IST | Sha Jan 16 |
Adar | Sunday, February 14, 2010 | 2:07 PM IST | Sun/Mon Feb 14/15 |
Nisan | Monday, March 15, 2010 | 2:51 PM IST | Tue, Mar 16 |
Iyar | Wednesday, April 14, 2010 | 4:35 AM IDT | Wed/Thu Apr 14/15 |
Sivan | Thursday, May 13, 2010 | 5:19 PM IDT | Fri May 14, 2010 |
Tamuz | Saturday, June 12, 2010 | 6:03 AM IDT | Sha/Sun Jun 12/13 |
Av | Sunday, July 11, 2010 | 6:47 PM IDT | Mon, Jul 12 |
Elul | Tuesday, August 10, 2010 | 7:31 AM IDT | Tue/Wed Aug 10/11 |
This table shows the actual (astronomical) time of the new moon (conjunction) in Israel Time. This can be gotten from a number of tables, such as the Naval Observatory time showed in the previous posting.
Astronomical Conjunction chart for 5770
Month | Date | Israel Time |
Cheshvan | Sunday, October 18, 2009 | 7:33 AM IST |
Kislev | Monday, November 16, 2009 | 9:14 PM IST |
Teves | Wed, December 16, 2009 | 12:39 AM IST |
Shvat | Friday, January 15, 2010 | 1:23 PM IST |
Adar | Sunday, February 14, 2010 | 2:07 PM IST |
Nisan | Monday, March 15, 2010 | 2:51 PM IST |
Iyar | Wednesday, April 14, 2010 | 4:35 AM IDT |
Sivan | Friday, May 14, 2010 | 5:19 PM IDT |
Tamuz | Saturday, June 12, 2010 | 6:03 AM IDT |
Av | Sunday, July 11, 2010 | 6:47 PM IDT |
Elul | Tuesday, August 10, 2010 | 7:31 AM IDT |
Calculated Average Molad chart for the year 5771
| Month | Day | Molad | Israel Clock Time | Rosh Chodesh |
Cheshvan | 30 Tishri 5771 Fri 8 Oct 2010 | 08:20:02 AM | 7:59 AM IST | Fri/Sha Oct 8/9 |
Kislev | 30 Cheshvan 5771 Sat 6 Nov 2010 | 09:04:03 PM | 8:43 PM IST | Sun/Mon Nov 7/8 |
Teves | 29 Kislev 5771 Mon 6 Dec 2010 | 09:48:04 AM | 9:27 AM IST | Tue/Wed Dec 7/8 |
Shvat | 29 Teves 5771 Tue 4 Jan 2011 | 10:32:05 PM | 10:11 PM IST | Thu Jan 6 |
Adar I | 29 Shevat 5771 Thu Feb 3 2011 | 11:16:06 AM | 10:55 AM IST | Fri/Sha Feb 4/5 |
Adar II | 28 Adar A 5771 Fri March 4 2011 | 12:00:07 AM | 11:39 PM IST | Sun/Mon Mar 6/7 |
Nisan | 28 Adar B 5771 Sun April 3 2011 | 12:44:08 PM | 1:23 AM IDT | Tue Apr 5 |
Iyar | 29 Nisan 5771 Mon May 3 2011 | 01:28:09 AM | 2:08 AM IDT | Wed/Thu May 4/5 |
Sivan | 28 Iyar 5771 Wed June 1 2011 | 02:12:10 PM | 2:52 PM IDT | Fri June 3 |
Tamuz | 29 Sivan 5771 Fri July 1 2011 | 02:56:11 AM | 3:36 AM IDT | Sha/Sun July 2/3 |
Av | 28 Tamuz 5771 Sat July 30 2011 | 03:40:12 PM | 4:20 PM IDT | Mon Aug 1 |
Elul | 29 Av 5771 Mon Aug 29 2011 | 04:24:13 AM | 5:04 AM IDT | Tue/Wed Aug 30/31 |
Dr. Roy Hoffman of the Israel new Moon Society has said that
The best time to see the crescent Moon, according to my research ("Observing the new Moon" R. E. Hoffman, Monthly Notes Roy. Astron. Soc., 340, 1039-1051 (2003).), is 0.6 of the time between Sunset and Moonset. The first crescent Moon appears between 15 and 55 hours after the true conjunction.
He has published predictions of possible first sightings of the new moon at
You can download my predictions for the next year at http://chem.ch.huji.ac.il/nmr/foo/handouts/5771e.pdf, and for last year at http://chem.ch.huji.ac.il/nmr/foo/handouts/5770e.pdfSome of these estimates show that the moon would definitely not be visible to the naked eye at that time.
I should point that that as Dr. Hoffman says
I do not publish calendars based on sightings because we are commanded to use our calculated calendar until a recognized Sanhedrin rules otherwise. If you do publish such a calendar, it is more than likely that a few individuals will follow it in contradiction to the halakhah.
Rosh Hashanna of 5772 will be Thu/Fri Sept 29/30
The actual conjunction and the possible “first visibility” list is shown below.
Note that the first visibility range is delayed because the first date is October 8, 5:16 PM – 5:26 PM. This is probably too short a time to actually see the moon. The following month, the first moonrise is at 4:45 PM which is less than ten hours. If the moon is seen on or before day 29 of the month, then the Sanhedrin would be able to declare the next day Rosh Chodesh and the previous month would be a 29 day month. Otherwise, the previous day would be a two day Rosh Chodesh by default. This occurs for Chesvan and Kislev. Note that Teves has two possibilities. If witnesses see the moon at the first available date (Dec 6), then Dec 7 would be the only day of Rosh Chodesh, unlike the calculated calendar which has two days. This would make the fast of Asara B'Teves occur one day earlier, Thursday, December 16, instead of Friday, December 17. This would also affect the declaration of the month of Shvat. Since it is the middle of the rainy season, it is very probable that the witnesses would miss the first sighting of the moon, forcing Teves to have tw days of Rosh Chodesh, just like the calculated calendar.
If Teves only had one day of Rosh Chodesh (December 7), then January 5 would be day number 30 of that month. This would force Shvat to have a two day Rosh Chodesh and would bring it back in sync with the calculated calendar.
Adar II now has two possibilities again because of the end of the rainy season. It is also possible that it would be missed because of the early time within the rang that the visibility occurs (19 hours 18 minutes). If it were visible, the Sanhedrin might deliberately not hold court because it would force Purim to occur on Shabbos. This affects Nisan, just as Teves did Shvat.
Note that Daylight Savings Time in Israel starts April 2. Thus, All time from April on are in Daylight Savings Time.
Nisan now has three possibilities because of the tw possibilities of Adar II. If Adar II had only one day Rosh Chodesh, then Nisan is forced to have two days Rosh Chodesh and comes back into sync with the calculated calendar. This is the same situation as if Adar II had two days Rosh Chodesh and the witnesses saw the moon in time for Nisan to have one day Rosh Chodesh. It is probable that they would see it as the moon would be 26 hours old. If they do not see it, Nisan has two days Rosh Chodesh and Pesach becomes Wednesday April 20 instead of Tuesday April 19. This is a significant effect and shows why we need the calendar to be precise. This also shows the reason for two days of Yom Tov in Chutz La'Aretz.
Iyar can now be either a one day or two day Rosh Chodesh depending on what had happened with Nisan (assuming that the witnesses do see the moon at the designated time. If they miss the moon, it would of course be forced to be a two day Rosh Chodesh.
Because Shavuos is defined as being counted from Pesach, the date would have been defined by what happened to Nisan.
Had Iyar had a single day of Rosh Chodesh, June 2 would have been the thirtieth day of the month forcing two days of Rosh Chodesh whether the moon was seen or not. If there had been two days of Rosh Chodesh, it would have again depended on whether or not the moon had been seen. This would set up three possibilities.
This sets up three possibilities for Sivan, but the first of Sivan woul occur on either June 3 or 4. This leads to Tamuz having one or two days Rosh Chodesh, but in either case, the first of the month is July 3. This brings it back in sync with the calculated calendar.
Av can now have one or two days Rosh Chodesh, meaning that Tisha B'Av can be on August 9 or 10.
While the moon on the day of the conjunction of Elul (Aug 29) may be visible, the time interval is only two minutes so it would probably be too close to the sun. If we assume that the second interval is seen, then the first of Elul is on the same day in either case. This allows Rosh Hashana to start as expected by the calculated calendar. On the other hand, if that day is not seen, Elul starts even later and causes a problem with Rosh Hashana because Elul 29 is pushed forward to September 29.
The Conjunction for Rosh Hashana 5772 is September 27 at 2:09 Am, with a possible visibility at 6:45 PM on September 28 (40 h 36 m moon age). This is Elul 29 according to the analysis above, which would make Rosh Hashanna occur on September 29 and 30. This is the same as determined by the calculated calendar.
| Month | Conjunction | Visibility Range | “best Time” (.6 of way) | Rosh Chodesh |
Cheshvan | Thu, Oct 7, 2010 8:44 PM IST | Oct 9 5:14 – 6:10 PM | 5:47 PM 45 h 3 m | Fri/Sha Oct 8/9 |
Kislev | Sat, Nov 6, 2010 6:52 AM IST | Nov 7 4:45 – 5:36 PM | 5:15 PM 34 h 23 m | Sun/Mon Nov 7/8 |
Teves | Sun, Dec 5, 2010 7:36 PM IST | Dec 6 4:35 – 5:14 PM | 4:58 PM 21 h 22 m | Tue Dec 7 |
Teves | Sun, Dec 5, 2010 7:36 PM IST | Dec 7 4:35 – 6:16 PM | 5:35 PM 46 h 50 m | Tue/Wed Dec 7/8 |
Shvat | Tue, Jan 4, 2011 11:03 AM IST | Jan 4 4:48 – 5:00 PM | 4:55 PM 5 h 52 m | Too early to see |
Shvat | Tue, Jan 4, 2011 11:03 AM IST | Jan 5 4:49 – 5:59 PM | 5:31 PM 30 h 28 m | Wed/Thu Jan 5/6 |
Shvat | Tue, Jan 4, 2011 11:03 AM IST | Jan 5 4:49 – 5:59 PM | 5:31 PM 30 h 28 m | Thu Jan 6 |
Adar I | Thu, Feb 3, 2011 4:31 AM IST | Feb 3 5:15 – 5:45 PM | 5:33 PM 13 h 2 m | Too early to see |
Adar I | Thu, Feb 3, 2011 4:31 AM IST | Feb 4 5:16 – 6:39 PM | 6:15 PM 13 h 44 m | Fri/Sha Feb 4/5 |
Adar II | Fri, Mar 4, 2011 10:46 PM IST | Mar 5 5:40 – 6:20 PM | 6:04 19 h 18 m | Sun Mar 6 |
Adar II | Fri, Mar 4, 2011 10:46 PM IST | Mar 6 5:40 – 7:13 | 6:35 PM 43 h 49 m | Sun/Mon Mar 6/7 |
Nisan | Sun, Apr 3, 2011 5:32 PM IDT | April 4 7:00 – 7:57 PM | 7:34 PM 26 h 2 m | Mon/Tue Apr 4/5 |
Nisan | Sun, Apr 3, 2011 5:32 PM IDT | April 4 7:00 – 7:57 PM | 7:34 PM 26 h 2 m | Tue Apr 5 |
Nisan | Sun, Apr 3, 2011 5:32 PM IDT | April 5 7:01 – 8:52 PM | 7:37 PM 50 hours 5 m | Tue/Wed Apr 5/6 |
Iyar | Tue, May 3, 2011 9:51 AM IDT | May 3 7:20 – 7:42 PM | 7:33 PM 9 h 42 m | Too early to see |
Iyar | Tue, May 3, 2011 9:51 AM IDT | May 4 7:21 – 8:39 | 8:07 PM 34 h 16 m | Wed/Thu May 4/5 |
Iyar | Tue, May 3, 2011 9:51 AM IDT | May 4 7:21 – 8:39 | 8:07 PM 34 h 16 m | Wed May 4 |
Sivan | Thu, Jun 2, 2011 12:03 AM IDT | Jun 2 7:40 – 8:21 PM | 8:04 PM 20 h 1 m | Thu/Fri June 2/3 |
Sivan | Thu, Jun 2, 2011 12:03 AM IDT | Jun 2 7:40 – 8:21 PM | 8:04 PM 20 h 1 m | Fri June 3 |
Sivan | Thu, Jun 2, 2011 12:03 AM IDT | Jun 3 7:40 – 9:12 PM | 8:35 PM 44 h 32 m | Fri/Sha June 3/4 |
Tamuz | Fri, Jul 1, 2011 11:54 AM IDT | July 2 7:49 – 8:39 | 8:19 PM 32 h 25 m | Sha/Sun July 2/3 |
Tamuz | Fri, Jul 1, 2011 11:54 AM IDT | July 2 7:49 – 8:39 | 8:19 PM 32 h 25 m | Sun July 3 |
Av | Sat, Jul 30, 2011 9:40 PM IDT | July 31 7:37 – 7:55 PM | 7:47 PM 22h 7 m | Mon Aug 1 |
Av | Sat, Jul 30, 2011 9:40 PM IDT | Aug 1 7:36 – 8:32 PM | 8:09 PM 46 h 29 m | Mon/Tue Aug 1/2 |
Elul | Mon, Aug 29, 2011 6:04 AM | Aug 30 7:06 – 7:42 | 7:27 PM 37 h 23 m | Tue/Wed Aug 30/31 |
Elul | Mon, Aug 29, 2011 6:04 AM | Aug 30 7:06 – 7:42 | 7:27 PM 37 h 23 m | Wed Aug 31 |
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