BLESSING THE SUN --------------- John Pazmino NYSkies Astronomy Inc www.nyskies.org email@example.com 2009 May 9 initial 2009 August 22 current
Introduction ---------- On Monday and Tuesday, April 6 and 7, 2009, several Jewish friends called my attention to a ritual that occurs only once each 28 years. The ceremony is Birkat Hachama (BEER-kaht hah-chah-MAH), Blessing the Sun. They asked if I knew about it and could explain the astronomy behind it. Because it comes around once per generation, many folk never heard of it before now. Other Jewish friends elaborated about the ritual and pointed out interesting tradition and astronomy in it. In 2009 it occurred at sunrise on Wednesday 8 April. The previous instance was on 1981 April 8. I can not recall anything of the 1981 round. The next instance is 2037 April 8. Thus, a given person can enjoy three, likely at most, Birkat Hachama events. There was extra attention and awareness in 2009 because Birkat Hachama occurred on the eve of Passover, an annual holiday of major importance for Jews. Thus, in this specific year of 2009, Jews got a double treat of astronomy within the same calendar day.
Ceremony ------ Birkat Hachama has various spelling in the Latin alphabet, much like other Hebrew words, because there is no uniform scheme of translitterating the Hebrew sounds into Latin characters. A similar situation applies to other languages that do not employ the Latin alphabet like Chinese, Arabic, Russian. Descriptions of Birkat Hachama commonly cross-reference other spellings. Birkat Hachama thanks the Sun for its benefit for humankind, as part of the works of Creation. The ceremony technicly is conducted when the Sun is at the place and time he occupied when he was formed during the Creation. This is when the vernal equinox occurs at sunset on a Tuesday. The Sun is not visible then for having just set. The ceremony is held on the first occasion that the new-born Sun comes into view, the very next sunrise on Wednesday. The coincidence of time and place comes at intervals of 28 years. In the other years, the Sun comes to the same place, the vernal equinox, but not the time, sunset on Tuesday, or to the same time but not place. The ritual is a gathering of Jews at or shortly after sunrise on the special Wednesday to recite certain Psalms and other odes. They offer gratitude to the works of Creation, specially to the Sun. Some Jews explain that it is not proper to praise the Sun at other times, like at every sunrise, because it looks like idolatry and object worship. The intent of Birkat Haxhama is to thank the creation of the Sun at special instances. Practice, at least in New York, varies among congregations. In the usual scene, the group meets at a synagogue or temple and stands in the shine of the Sun. It does not necessarily gaze at him but lets his rays fall on it. If the sky is cloudy, as it was in New York on April 8th near sunrise, the group stands in open air where a Sun in the clear would shine on it. In a couple cases on Manhattan, due to high skyline, the group went to a nearby street corner for a sight line to the Sun. Only under extremely adverse weather, a storm, may be ceremony be performed indoors. Some groups require in this case that they look out a window facing the Sun. Some groups require that the ceremony complete within a stated period after sunrise. Others allow the ritual to procede at its own pace. SInce the odes are short and can be recited quickly, there seems to be problem to complete the celebration within a reasonable time. The odes my be recited in either Hebrew or the native language. for New York, Hebrew is a common tongue among Jews, but it is good enough to sound out the Hebrew words from an phonetic script in the native language. The groups disbanded after the ritual, not to convene again until the next round. The elder Jews welcomed the younger ones into the ritual and reminded these young ones to carry the tradition forward. It is possible that the current elders will no longer be around on the next celebration, 28 years later in 2037.
Creation ------ Birkat Hachama comes from the traditional story of Creation. For most Jews it is merely a cultural event, without implying the reality of the Creation story. Some Jews, however, sincerely believe that the Biblical story is a genuine history. In the beginning there was Nothing. Then, at sunset on day #1 there sprang forth Light. This moment is the first hour of the first day of the first month of the first year in the Jewish calendar. In modern notation, this was sunset (the first hour of the Jewish day) on Sunday 1 Nisan, year 1. Like just about all ancient cultures, the counting starts at '1', not '0'. Jews still maintain this calendar, along side the civil calendar, so that the year count by 2009 is up to 5769. That is, the cosmos was born 5,768 years ago. We were in the 5,769th year of the world when this year's Birkat Hachama took place. In modern chronology, the Creation began on -3760 April 13 on the Julian calendar. For dates before Caesar back into the indefinite past the Julian calendar is applied. This method gives a consistent, if artificial, dating to historical events that can be manipulated by calendar maths regardless of the era. The cosmos developed day by day until day #4. At the sunset that initiated day #4 the Sun, Moon, stars, and planets were born. The Sun at this moment was placed at the vernal equinox point. He stood over the Earth's equator passing from south to north. This moment is the beginning of day #4, in hour #1, and also the beginning of the spring season on Earth. I here use the modern names for the weekdays. Many Jews go by day number. The week starts with Sunday, the first day of the world and ends on Saturday, the Sabbath, when all the Creation was finished. Day #4 is Wednesday. Birkat Hachama takes place when the Sun is again at BOTH the vernal equinox AND the start of day #4. This aspect simulates the conditions during the week of Creation. That is, the Sun must be at the vernal equinox point and also set on Tuesday, which is when Jewish day #4 starts. Since the Sun wasn't born yet for days 1 thru 3, the clock hours and day counts for events in these days are proleptic. Until the Sun and stars came along, the world was black with no way to count days or hours in any conventional manner. Jewish scholars speak of a virtual clock, somewhat the way cosmologists today work with a cosmic time keeping scheme. Creation continued for several more days, culminating in the placement of humans on Earth in the sixth day. The seventh day, the Sabbath, was when the world had its first rest from the tasks and chores of being created. There after, the rest is history. The concept of a day of rest was almost a unique feature among jews. Just about all other peoples worked every day without setting a definite time for rest. Such a practice of suspending work on the Sabbath, every seventh day, was often deemed an act of laziness or slothfulness by outsiders.
Vernal equinox ------------ When the Sun and other celestial bodies were born, they were in animation in their paths thru the stars. At the moment of his creation the Sun was over the equator of Earth on his way from the southern hemisphere to the northern. This moment and place in the stars is the vernal equinox and is for the northern peoples the first day of the spring season. The Sun's path is essentially a fixed great circle across the heavens, inclined 23-1/2 degree to the Earth equator. In terms of the day, the fundamental unit of time from antiquity all the way to the mid 20th century, the Sun takes about 365-1/4 days to do one lap of the heavens and return to the vernal equinox point. This is the year. For peoples in the mid northern latitudes, the cycle of the Sun from vernal equinox and return matched the cycle of the seasons, the flow and ebb of the bioculture that sustained them. Spring, occurring near the vernal equinox, started a new round of life and growth after the cold and inertia of winter. This correlation of solar motion and seasonal cycle caused most early cultures to start a new year at or near the vernal equinox. The early Jews and the Babylonians from whom they borrowed much of their astronomy, knew quite well that the year is actually a trifle less than 365-1/4 day. he Jews settled on the rounded number for simplicity of calculation. By and by, they linked their chronology to the Julian calendar. On this calendar the vernal equinox occurred on March 25. This is a few days later than the current date of March 20, due to accumulated discrepancies between the Julian and Jewish year of 365- 1/4 day and the true year length. Altho the small discrepancy builds up over the ages, sliding the vernal equinox to March 18 Julian, the Jews keep the March 25 historical date to calculate Birkat Hachama. Jewish scholars explain that Birkat Hachama is a cultural, not an astronomy, celebration. In addition, there is nothing special about the arrangement of the other planets, stars, Moon. The Moon, the body that governs the Jewish calendar, is disregarded for Birkat Hachama. The vernal equinox occurs at an instant that varies year to year. For Jewish calendar purposes the vernal equinox is set at only one of four hours. These are 00:00 (in civil time), 06:00, 12:00, and 18:00. These steps correspond to the 1/4 day extra each year over the 365 full days. These hours correspond about to midnight, sunrise, noon, and sunset. Because the Jewish day begins at sunset, these hours are the 6th, 12th, 18th and 0th hour of a Jewish day. Except for critical situations, in the mid northern latitudes sunset is schematized to occur at 18:00 all year round. Thus, the equinox may be at 06:00 in the first year, but must then occur at 12:00 in the next, 18:00 in the third, and 00:00 in the fourth. But by then the 1/4 days build to a full day, calling for the leapday in the Julian calendar. In this way the equinox is preserved with the same calendar day and the seasons stay lined up with the other months of the year. In spite of the tiny but continual accumulation of discrepancy of the rounded and true length of the year, the Jews keep March 25, Julian, as the date of the vernal equinox. Jewish scholars know that this does not agree with the astronomy date of the equinox, nearer to Julian April 4 in the 21st century.
Julian Calendar ------------- The Julian calendar is arranged into twelve months of 30 or 31 days, as developed by Julius Caesarand amended by Augustus Caesar. The year then began with March and ran thru february. This history is reflected in the 'number' months like October. October is no longer the 8th month, its original standing in the year. The Julian year has 365-1/4 days. The 30/31 day arrangement of the months left a fractional month at the end. This, February, had only 28 days. To honor his work, Julius renamed the fifth month after himself, our July. Julius accounted for the extra quarter day by adding a full day every four years, He tacked this leapday to the end of the year, making 29 days for February. When the custom deve[oped of starting the year in January, the leapday stayed with February, now an interior month of the year. Augustus Caesar amended the calendar to remove some mistakes in counting and took the sixth month to honor him, August. This is how the months are arranged thru today. Since Augustus's time, the early years of the first century, the revamped Julian calendar remained on track. Some cultures still use it today parallel to the civil calendar. The mechancial addition of leapdays every fourth year, in the years evenly divisibe by 4, inserted too many extra days. The vernal equinox slided back in date by one day every 128 yers. The vernal equinox, on March 23 in Augustus's time, by now is on March 8 Julian. The rule-of-four for Julian leap year is an absolute quirk of history. Augustus and later emprorers use various counts of years, none related to the way leap year was announced. When the present AD scheme of year count was adopted, it was discovered that leap year was in the years whose number was divided evenly by four. It sure didn't have to happen this way! For years BC the algebraic count is empluted: 0, -1, -2, ^c. This simplfies calendar calculations and also preserves the rule-of-four into the infinite past. (Year 0 divided by 4 is 0 with no remainder.)
Jewish calendar ------------- The Jewish calendar is a lunisolar system of twelve months based on the cycle of lunar phases and adjusted periodicly to realign with the solar year. However, no actual year has 365 or 366 days. The year averages out to this length over a cycle of 19 years by the addition of leap months and jiggering the days within certain months. Before the 4th century the Jewish calendar was managed locally by each community, resulting in erratic dating of events. Conversions to and from Jewush dates are now done with the modern scheme. For earlier epochs, this system is prolonged back in time, like the retrolongation of the Julian calendar to eras before Julius Caesar. In primitive times the month began when a dedicated skywatcher declared that he saw the firstn cescent after New Moon. This is First Moon and is still the official way some peoples today initiate a new month. It didn't take long to systematize the month start to a standard rule without relying on weather and eyesight to catch the first glimpse of the nww cycle of phases. The modern Jewish calendar has months of fixed or regulated number of days. The Jewish year starts with the month of Nisan near the vernal equinox. In the Creation the cosmos came into being on 1 Nisan at 18h civil time of Saturday 13 April -3760. This was also the zeroth hour of Sunday. The twelve lunar months total 354 days, 11-1/4 days short of the solar year. After a few years an extra, leap, month Adar II is added at the end of the year. With Adar II the Jewish year has 384 days. There are some other adjustments from year to year such that the length varies a day or two from these values. The insersion of Adar II and other adjustments are strictly regulated such that the sequence of changes repeats every 19 years. In this span, there are 6939-3/4 days and 235 lunar phase cycles of 29.53 days. The latter is built from appropriate mix of 29 and 30 day months. This is why on the civil calendar the Jewish holidays seem to slide around year to year. Within the Jewish calendar the holidays are spaced at stated intervals downrange from 1 Nisan. In the last month or two of the Jewish year the dates get irregular but there are no significant holidays then. The Jews celebrate two New Years. One is on 1 Nisan. The other, more common in modern times, is on 1 Tishri, the xeventh month. It is also the practice to index the year at this second New Year, on Rosh Hashanah. In this sense, Tishri can be the first month and Nisan, in the middle of the year, is the 7th (8th with Adat II) month, The year ends with Elul just before the next Tishri. It is at i Tishri, not 1 Nisan, that the year count changes. A date in Elul is in one year and one in Tishri is in the next year.
Day count ------- The Jews count days from sunset, not midnight. The date and day changes then so the afternoon is in one and the twilight and night are in the next. This is why the Jews start celebrating a holiday on the evening before the civil date. In 2009, as example, Passover begins on Thursday 9 April. The actual start of 'April 9' in the Jewish reckoning was at sunset of April 8th. That's when the first events of Passover took place. Practice varies to count from the actual sunset, according to the season, or to schematize the sunset at 18:00 (civil time) all year round. In places that block view of the Sun or got persistently cloudy skies the 18:00 schematic sunset seems the better option. It is also the option where Jews interact strongly with the civil society. In spite of counting days from sunset to sunset, I'm not aware of a Jewish clock ticking on this system. The clock hour in all Jewish writings I ever saw follows the civil clock. A certain meeting is booked for '21:30 on April 8th'. This means NOT 21:30 after sunset (which is when the instant day began), but 21:30 from the preceding midnight, or about 03:30 after sunset. On the other hand, I do see that the number of the day sometimes is changed at sunset, so the hours before then are in one day number, like April 7th, and those after are in the next day number, April 8th. Absolutely ridiculous mixups can happen if the method is not carefully stated. It's like the confusion of when '12 AM' or '12 PM' occur.
Weekdays ------ When the Sun was born on the 4th day of Creation, so were the planets, Moon, and other objects in the heavens. To honor the formation of the planets, the first hour of the fourth day was given to the Moon, the first planet visible in twilight, before the sky darkened enough to reveal the others. This means a virtual sighting of the Moon, there not yet being humans on Earth to physicly witness her. The second hour (19h civil) was given to the highest, farthest, planet to take care of. This was Saturn. The third hour (20h civil) was Jupiter's watch. Then Mars, Sun, Venus, Mercury, and Moon. The rank of planets inward toward earth was based on the apparent angular speeds thru the stars. Saturn moved the slowest; Moon, fastest. After the Moon, the round of planets repeated. like the at-bat lineup of a baseball game. After three complete rounds of planets, there were three more hours left to start the fourth round. The The last hour, 23h civil, was looked over by Venus, and the very next hour, the zeroth hour of the next civil day, went to Mercuty. After seven days of 24 hours each, the zeroth hour of the next day was again assigned to Saturn and the whole cycle began again for the next seven days. This is how the 7-day week was created. The name of the weekday is that of the planet watching over its first, zeroth, civil hour. At the midnight of the civil day on which the Sun was born, Mercury took over the zeroth hour. That day was Mercury's day, Mercurii Dies in Latin, our Wednesday. Jupiter handled the zeroth hour of the next day, Jovis Dies, Thursday. The last day of the week was ushered in by Saturn's care of its zeroth hour. This was Saturday, Saturni Dies, the Sabbath or Day oF Rest. This scheme is tabulated here. The planets are given their Latin abbreviations.
----+-----+-----+-----+-----+-----+-----+-----+-----+--------- hr | Sat | Sun | Mon | Tue | Wed | Thu | Fri | Sat | Jewish ----+-----+-----+-----+-----+-----+-----+-----+-----+--------- 00 | Sat | Sol | Lun | Mar | Mer | Jup | Ven | Sat | 06 | 01 | Jup | Ven | Sat | Sol | Lun | Mar | Mer | Jup | 07 | 02 | Mar | Mer | Jup | Ven | Sat | Sun | Lun | Mar | 08 | 03 | Sol | Lun | Mar | Mer | Jup | Ven | Sat | Sol | 09 | 04 | Ven | Sat | Sol | Lun | Mar | Mer | Jup | Ven | 10 | 05 | Mer | Jup | Ven | Sat | Sun | Lun | Mar | Mer | 11 | 06 | Lun | Mar | Mer | Jup | Ven | Sat | Sol | Lun | 12 THIS 07 | Sat | Sol | Lun | Mar | Mer | Jup | Ven | Sat | 13 day 08 | Jup | Ven | Sat | Sol | Lun | Mar | Mer | Jup | 14 | 09 | Mar | Mer | Jup | Ven | Sat | Sun | Lun | Mar | 15 | 10 | Sol | Lun | Mar | Mer | Jup | Ven | Sat | Sol | 16 | 11 | Ven | Sat | Sol | Lun | Mar | Mer | Jup | Ven | 17 | 12 | Mer | Jup | Ven | Sat | Sun | Lun | Mar | Mer | 18 | 13 | Lun | Mar | Mer | Jup | Ven | Sat | Sol | Lun | 19 | 14 | Sat | Sol | Lun | Mar | Mer | Jup | Ven | Sat | 20 | 15 | Jup | Ven | Sat | Sol | Lun | Mar | Mer | Jup | 21 | 16 | Mar | Mer | Jup | Ven | Sat | Sun | Lun | Mar | 22 | 17 | Sol | Lun | Mar | Mer | Jup | Ven | Sat | Sol | 23 \|/ ----+-----+-----+-----+-----+-----+-----+-----+-----+--------- 18 | Ven | Sat | Sol | Lun | Mar | Mer | Jup | Ven | 00 /|\ 19 | Mer | Jup | Ven | Sat | Sun | Lun | Mar | Mer | 01 | 20 | Lun | Mar | Mer | Jup | Ven | Sat | Sol | Lun | 02 NEXT 21 | Sat | Sol | Lun | Mar | Mer | Jup | Ven | Sat | 06 day 22 | Jup | Ven | Sat | Sol | Lun | Mar | Mer | Jup | 04 | 23 | Mar | Mer | Jup | Ven | Sat | Sun | Lun | Mar | 05 | ----+-----+-----+-----+-----+-----+-----+-----+-----+---------
Over the ages various calendars were promulgated by various cultures. Months, day count, dates, year count were adjusted and altered. Such mutations of chronology is one of the massive problems historians and archaeologists face to map the history of peoples. The circuit of weekdays remained stable since the beginning of the world. There never was any serious effort to add, remove, alter, shuffle the weekdays. They march on and on, planet after planet, day after day, across the ages.
Cycles ---- By the sequence of the Creation, the Sun was born at sunset, the 18th civil hour of Tuesday, the zeroth hour of Wednesday as the fourth day, and was placed in his vernal equinox position. On the Jewish calendar the Sun ws formed at the start of 4 Nisan, while the universe itself came about on 1 Nisan. This inaugurated year #1 in Jewish history, with this year of 2009 being the 5,769th since then. Birkat Hachama is performed when these two factors next occur. I didn't discover the first documented celebration of Birkat Hachama, but it was likely conducted at least since the Roman era. I did find a news account of the first recorded (but not necessarily first observed or practiced) instance on Manhattan. On 1897 April 8 a group of Jews celebrating in Tompkins Square was disbanded by police for lacking an assembly permit. The police didn't understand the event, accepted that it was a peaceful one, yet noted that it still needed a permit. Recall that the Jewish year has exactly 365-1/4 day and that the vernal equinox is schenatized to occur only at 00:00 (civil time), 06:00, 12:00, 18:00. Each year, because of the extra quarter day, the vernal equinox notches six hours later on the calendar. When these amount to one full day, the Julian scheme adds a laepday, keeping the vernal equinox within the same calendar day. If the vernal equinox fell at sunset on Tuesday in one year, when will it again do that? The table here gives the sequence of the two events from 1981 thru 2037, covering two Birkat Hachana intervals.
-------+------+------+------+------+------+------+------ hour | Tue | Wed | Thu | Fri | Sat | Sun | Mon -------+------+------+------+------+------+------+------ 18:00 |*1981*| -- | -- | -- | -- | -- | -- -------+------+------+------+------+------+------+------ 00:00 | 1986 | 1998 | 1982 | 1994 | 2006 | 1990 | 2002 06:00 | 2003 | 1987 | 1999 | 1983 | 1995 | 2007 | 1991 12:00 | 1992+| 2004+| 1988+| 2000+| 1984+| 1996*| 2008+ 18:00 |*2009*| 1993 | 2005 | 1989 | 2001 | 1985 | 1997 -------+------+------+------+------+------+------+------ 00:00 | 2014 | 2026 | 2010 | 2022 | 2034 | 2018 | 2030 06:00 | 2031 | 2015 | 2027 | 2011 | 2023 | 2035 | 2019 12:00 | 2020+| 2032+| 2016+| 2028+| 2012+| 2024+| 2036+ 18:00 |*2037*| 2021 | 2033 | 2017 | 2029 | 2013 | 2025 -------+------+------+------+------+------+------+------
The leap years are marked with a '+'. Note carefully that year 2000 was a leap year because it was an even multiple of 400. This is a feature of the Gregorian calendar, that supplanted the Julian calendar for just about all civil purposes. The vernal equinox occurs every year, but on different days and hours. It occurs at sunset (18:00 civil time) on Tuesday (civil day, start of Jewish day #4) only at intervals of 28 years. For most Jews, there are three, possibly four, occurrences within a lifetime. A 1-year-old person in 1981 would be 57 years old for the 2037 celebration and 85 for the one in 2065. This year's Birkat Hachama is the 206th since Creation. There apparently was no Birkat Hachama on the very day the Sun was born because there was no human on Earth yet to celebrate it.
Passover ------ Passover is set for the first full Moon after the vernal equinox. The vernal equinox is still the schematic March 25 Julian, but the full Moon can occur any number of days there after from the very day of the equinox to almost a full lunation later. This latter happens if there was a full Moon on the day before the equinox. It is revoltingly tough to tell just when the Moon is exactly full with no optical assistance. The Moon looks pretty nice and round a day or two around the geometric Full Moon moment. Besides that, the full Moon could happen in an other timezone, out of sight of the local Jews. They see it either too early on the previous night or too late on the next night. To get around these difficulties, the Jews put the full Moon to be on 15 Nisan, regardless of her actual aspect. Since 1 Nisan begins when at First Moon is sighted, usually one day after New Moon, this is a reasonable work around. Full Moon does occur about 15 days after New Moon, or 14 after the first sighting. For calculating Passover a floating vernal equinox is used, not a fixed one like the March 25th for Birkat Hachama. Passover by Jewish tradition must always come after the equinox, but with a short year of twelve lunar months, 15 Nisan could in some years fall before then. The addition of a thirteenth month, Adar II, from time to time by a strict schedule ensures that the vernal equinox occurs late in the instant year or early in the next, within one lunation. Then 1 Nisan can be safely observed as the First Moon after the equinox and Passover comes on the 15th of Nisan, well after the equinox. It is only chance that in this year of 2009 Passover comes on the same civil day, Wednesday 8 April, as Birkat Hachama. Coincidences are very irrgularly spaced, the last being in 1925. Some scholars noted that this was perhaps the closest interval between coincidences, the usual spacing is many, many centuries. The last instance before 1925 was in 1309 and then two in the 600s. There is no special significance to the joint events in 2009, except for the better attention steered to Birkat Hachama by the adjacent Passover. The table here gives the civil dates of equinox, First Moon (Nisan 1) and Passover (Nisan 15) for 2000-2020. Remember that the Jewish day starts at 18h civil on the previous date. Passover on 2009 started on Apr 8. Note that the equinox is starting to slide on the Gregorian calendar from March 20 to March 19. This is a long tern trend with more frequent March 19 dates later in the 21st century.
year | equinx | Nis 1 | Nis 15 | Jewish equinox ------+--------+--------+--------+-------------------------- 2000 | Mar 20 | Apr 6 | Apr 20 | Apr 7 Fri 12h leap year 2001 | Mar 20 | Mar 25 | Apr 8 | Apr 7 Sat 18h 2002 | Mar 20 | Mar 14 | Mar 28 | Apr 7 Mon 00h 2003 | Mar 20 | Apr 3 | Apr 17 | Apr 7 Tue 06h 2004 | Mar 20 | Mar 23 | Apr 6 | Apr 7 Wed 12h leap year 2005 | Mar 20 | Apr 10 | Apr 24 | Apr 7 Thu 18h 2006 | Mar 20 | Mar 30 | Apr 13 | Apr 7 Sat 00h 2007 | Mar 20 | Mar 20 | Apr 3 | Apr 7 Sun 06h 2008 | Mar 20 | Apr 6 | Apr 20 | Apr 7 Mon 12h leap year 2009 | Mar 20 | Mar 26 | Apr 9 | Apr 7 Tue 18h BH event 2010 | Mar 20 | Mar 16 | Mar 30 | Apr 7 Thu 00h 2011 | Mar 20 | Apr 5 | Apr 15 | Apr 7 Fri 06h 2012 | Mar 20 | Mar 24 | Apr 7 | Apr 7 Sat 12h leap year 2013 | Mar 20 | Mar 12 | Mar 26 | Apr 7 Sun 18h 2014 | Mar 20 | Apr 1 | apr 15 | Apr 7 Tue 00h 2015 | Mar 20 | Mar 21 | Apr 4 | Apr 7 Wed 06h 2016 | Mar 19 | Apr 9 | Apr 23 | Apr 7 Thu 12h leap year 2017 | Mar 20 | Mar 28 | Apr 11 | Apr 7 Fri 18h 2018 | Mar 20 | Mar 17 | Mar 31 | Apr 7 Sun 00h 2019 | Mar 20 | Apr 6 | Apr 20 | Apr 7 Mon 06h 2020 | Mar 19 | Mar 26 | Apr 9 | Apr 7 Tue 12h leap year ------+--------+--------+--------+--------------------------
The April 7 date of the Jewish equinox comes from the declared March 25 Julian plus 13 days lag behind Gregorian. (25 March) + (13) = (38 March) = (7 April). This date is 18 days after the astronomy equinox of March 20.
Gregorian calendar ---------------- In the Gregorian calendar the vernal equinox in 2009 fell on March 20th. This is 18 days earlier than Birkat Hachama, occurring on April 8th. The error is one of using a schematic calculation rather than one answering to the real motions of the Sun. Altho in early years, the equinox was on March 25 Julian (there being no Gregorian calendar yet). the Julian calendar used the 365-1/4 day length for the solar year. The fractional day excess over the true year length gradually shoved the equinox to March 11th by the 1500s. The Gregorian calendar of 1582 modified the Julian system by first removing the extra ten days to get the equinox back to March 21. This is where it was when the rules for Easter were worked out in the mid 300s. The day after 1582 October 4 is 1582 October 15. There are no valid dates between these limits. The Gregorian calendar also fixed the leapdays by omitting them from century years that are not even multiples of 400. 1600 and 2000 were leapyears, but 1700, 1800, 1900 were years of 365 days. Julian reckoning inserted leapdays in these years with the rule-of-four. These extra leapdays slided Julian three more days behind Gregorian since 1600 so that the total offset is now 13 days. Most of the Catholic countries made the change immediately. Many others took decades and centuries to change over. In astronomy it is usually assumed that the conversion took place all over the world at once, which can lead to erroneous results if the astronomer's site was still running the Julian system after 1582. Based on the astronomy vernal equinox, Birkat Hachama is celebrated way too late in the year. The Sun on April 8 at sunrise is about 19 degrees east of the vernal equinox and about 7 degrees north of the equator.
Rosh Hashanah ---------- In other parts of Jewish culture the world was created in the autumn, not spring. Rosh Hashanah celebrates this event as one of the major Jewish holidays. It occurs on 1 Tishri, the 7th Jewish month or the first counting from this New Year. Rosh Hashanah in 2009 is on 19 September. The year changes at Rosh Hashanah, not at 1 Nisan. In 2009 the year steps from 5769 to 5770. Like for all Jewish days, the observance starts on the previous evening at 18h civil. Some Jews treat Rosh Hashanah as the date the universe was planned 'on paper'. The creation in 'brick and mortar' came a half year later at the next 1 Nisan. The use of alternative New Years is not all that strange. hydrologists work with a water year from April to the following March in synch with the flow of rivers, at least in the mid north latitudes. Eclipse computations are based on a Bessel year, from when the Sun's longitude is 280 degrees to the next instance. This occurs near December 31. Schools start their year on September 1 to gear up for the actual start of classes a week or so later. Governments keep records in a payroll year of exactly 52 weeks, i day shorter than a calendar year. Two extra weeks are added every five or so years to get back in step. Businesses use a fiscal year that starts on April 1, July 1, or October 1. Club memberships commonly start on February 1 or March 1 to give time to process renewals that were due on January 1st. There seems to be no great debate among rank-&-file Jews about this dual New Year situation. Jewish scholars do have discussions but on the whole the status quo is accepted and left alone.
Conclusion -------- It'll be a while, until 2037, before we have the next Birkat Hachama. That is comes only once in a generation and only three, or possibly four, times in a lifetime, makes it a special event to look forward to. It added an extra element to this year's Passover, adding a positive enhancement to the Jewish experience. The loose astronomy, like the fixed ediurnate date for the equinox throws the aspect of the Sun in the sky away from what it was during the Creation. On the other hand, Jewish scholars recognize this defect and treat Birkat Hachama as a cultural ritual, not an astronomy event. No one I spoke with about Kirbat Hachama seemed to know of other astronomy-related or Creation-related celebrations with such a long interval between occurrences.