Thus all the passages in Sanskrit texts which describe planets in the week-day
order should be dated later than the end of the third century.
Graha worship section of the Gr.hyasu ̄tras Many variations of the order of the
ninegrahasare found in the section of the rite of worshiping grahas(grahayajña)
in the Gr.hyasu ̄tras. Thus the time in which this rite originated belongs to the
fourth stage mentioned above. Even in one and the same text we can find differ-
ent orders of enumeration. In some texts the seven planets are arranged in the
order of Sun, Mars, Moon, Mercury, Jupiter, Venus, and Saturn. Some texts pre-
suppose the week-day order using the word kramen.aorkrama ̄t(“by the order (of
week-day)”). Such texts or at least this part of such texts must be considered as
belonging to the later period.^4 Old elements are of course preserved and repeat-
edly appear in the later texts, so we cannot use such elements as the means of
fixing the lower limit of the date of a document, while new elements can surely
serve as the criterion to judge the upper limit of the text, or at least the part of
the text which contains them.
4 Classical Period
4.1 New aspects
Zodiacal signs A great change of the jyotih.s ́a ̄straresulted from the introduction
of Hellenistic astrology and astronomy into India. The most remarkable element
in this was the important role played by the seven planets. Other new elements
transmitted to India were the twelve zodiacal signs beginning with Aries and the
twelve astrological places beginning with the ascendant. The first point of Mes.a
(a translation of the Greek word corresponding to Aries) was equated with the
first point of the naks.atra As ́vinı ̄. With the relation 27 naks.atras =12 zodiacal
signs (i.e., 9/4 naks.atras =1 zodiacal sign), one zodiacal sign was equated to
“nine quarters” of a naks.atra.
Referring system The Sanskrit names for zodiacal signs are translations of the
Greek words and in some texts we find phonetic transliterations from Greek.
However, there is a remarkable difference between the western zodiacal signs
and Indian signs (called ra ̄s ́i). In Indian astronomy the precession (ayana) of
equinoxes was not taken into account and the initial point of the ecliptic coor-
dinates was fixed sometime about ad285.^5 This is the so-called nirayan.asystem.
In the course of time, therefore, the true vernal equinox (V.E. in figure 18.1),
moving backward, separated from the initial point (mes.a ̄di) of the nirayan.a
longitude. The amount of this difference, called ayana ̄m.s ́a, has accumulated
to some 23.5 degrees in modern times. This is the reason why the day of
384 michio yano