What's Your Sign?

Tomorrow is my birthday, July 11, and this got me thinking about whether the proper way for one to determine his astrological sign is to use his birthday based on the solar calendar, or if he should use the lunar month in which he was born. For me there would not be a difference because July 11 is Cancer and my Hebrew birthday, 6 Tammuz, also is in the month of Sartan (Cancer). However, because the start and end of the Hebrew months do not always occur on the same dates of the solar calendar, for some people the solar calendar would produce one sign for them and the Hebrew calendar another.

The standard way to refer to the astrological signs in Jewish literature has been to assign a sign to each month. Thus, Nissan is T'leh (Aries), Iyar is Shor (Taurus), etc. Using these references, one would have assumed that the Jewish system of astrological signs is not dependent on the solar calendar and that one would disregard his "English birthday" and only use his Hebrew birthday to determine his sign.

The reason why this might not be the case is because it is plausible that when Chazal mention that Nissan is T'leh, they only meant that on average the majority of Nissan is T'leh, but they really agree that the astrological signs are based on the solar calendar. Before you stop reading and wonder why I would make such an assertion, let me explain why this actually seems to be the way many Rishonim understand the system.

Rashi and the R. Avraham ibn Ezra both seem to suggest that the Jewish astrological system is really based on the solar calendar. When describing why each month has its specific sign, Rashi clearly mentions that it is based on the sun's position relative to the stars in the sky. (See Rashi Rosh Hashanah 11b; also see Rashi Rosh Hashanah 11a and Tosefos Rosh Hashanah 2b that mention that sometimes when Chazal refer to a month they are really referring to the corresponding solar month. ) This is a clear reference to the solar calendar as the lunar months would have no bearing on the sun's position in the sky. (Of course, axial precession has caused the apparent position of the stars to shift but that is a discussion for a different post.) The ibn Ezra's books on astrology, Reishis Chachmah and Sefer Hata'amim, also clearly indicate that the system is predicated on the solar calendar. If this is the case then it would seem that the proper way to determine one's astrological sign would be to take one's "English birthday" and not their Hebrew birthday.

Although the above seems to express the opinions of Rashi and the ibn Ezra, it is certainly not unanimously agreed upon by all Rishonim. When commenting on the passage from Beshalach that discusses the war with Amalek, the Chizkuni mentions that people born in the month of Adar II have no astrological sign whatsoever. There are only twelve signs and they have been "used up" by the time you get to the thirteenth month of the year!!! This explanation makes it very clear that the Chizkuni understands the astrological signs of Jewish people to be dependent on the Hebrew months and not the solar calendar.

Thus, it seems that there are two opinions as to how to determine one's astrological sign. As I mentioned above, for me the two systems yield the same result. However, for some people they may not really know which is their birth sign as there is a debate amongst the Rishonim as to how to determine it.