In India, Constellations, stars, planets and satellites are classified into two groups based on whether they affect earth and if so, whether the effect is continuously stable or variable. For easy comprehension, the effect is judged by the magnitude of their visibility under normal conditions, as it is determined by both their mass and relative distance. For this reason, the prominent Constellations and stars are called Nakshatras, that which affects the earth continuously with the same force from the same relative position. This has routine requirement in weather forecasting, besides some other cases. Sun and Moon are called Graha – that which affects the earth more or less equally (based on their respective mass and distance, as displayed by their visual size), but the influence varies over the day and months. Planets Mercury, Venus, Mars, Jupiter and Saturn are also called Graha for the same reason, as their relative position with respect to the Earth varies continuously. All other planets (including Uranus, Neptune and Pluto) and satellites are ignored as having insignificant influence on Earth, though comets that come near earth and influence it, are considered as Dhoomaketu.
The radiations coming to earth from all directions are called RASHI, which literally means heap, because they belong to various wavelengths. These have been classified into 12 parts based on the number of different wavelengths coming from each direction (actually, the number is six: one maxima, one minima, four intermediate), indicating a direction to the Cosmic Microwave Background. This is not the same as the division of the Zodiac. The day and night together is called AHORATRA. Hence half of a Rashi is called HORA, the middle part of A’HORA’TRA (this is because the length of day and night – hence its exposure to any Rashi, are variable in a specific sequence). This makes it 24 Hora in a day, which is called hour in the West. A Rashi is not related to the Zodiac, but to the Cosmic Radiation Background by treating the first point of Aries as its beginning. This point appears to change due to precession of equinoxes. However, since the background is fixed and the changes appear due to the motion of earth, the calculations are adjusted by making suitable corrections (NIRAYANA). The difference from its actual position is called Ayanamsha.
Between the Sun and the Earth, whether we calculate their relative position from the Sun or the Earth, mathematically, there is no difference. Hence, for ease of calculation, the Sun is substituted for Earth on many occasions. Instead of treating the period of revolution of Earth as 1 year, it is considered as the period of rotation of the Sun. For calculating the relative position of the inner planets, this formula is used. For calculating the relative position of other planets, this factor is taken into account with suitable modification. To account for the anomalous fluctuations of planetary and star perihelion’s (like that of Mercury solved first by Gerber and then by Einstein), the average rate of rotation of different stars, planets and satellites are considered over a period of 4.320 billion years (called BHAGANA). Then suitable adjustments are made to arrive at the actual position for any day (for inner planets it is called SHEEGHRA and others MANDOCHCHA). Since Moon is a satellite for earth and moves with it, it is placed in between Mars and Venus.
The earth could sustain life because of its relative position in the solar system, where the influences coming from the distant stars and outer planets are just balanced by the Sun and the inner planets. Since the earth is rotating continuously, it is subjected to the influence of GRAHAs differently, but in a sequence. Thus, for calculating the hora influence, the GRAHAs are arranged in a peculiar order: based on their orbital periods, but treating the Earth as the center of observation.
Thus, the sequence is:
- Sun,
- Venus,
- Mercury,
- Moon (Earth, from which the order reverses),
- Saturn,
- Jupiter,
- Mars,
For each Hora, the GRAHAs exert their influence cyclically in this order. The weekday is named after the GRAHA, whose influence is felt at Sunrise. Since the Sun is the most important factor in the solar system, the first hora of the first day of the week is attributed to it. Hence, the first day is called Sunday. The hora of other planets move in the above sequence. After completing 3 cycles, three more horas complete one day. Thus, the first hora of the next day is the fourth from Sun and the next day begins with the hora of Moon. Hence, the weekday is called Monday. The same order repeats for all weekdays.
The day in India begins at Sunrise. The average time in India is calculated from Ujjain, as it falls on the straight line joining Sri Lanka and the North Pole. During zero equinox, this line drawn as a perpendicular to the equator, points to the first point of Aries. All ancient Indian geographical descriptions followed this principle. Presently, the value of the precession of equinoxes is about 24° 06’ 29’’. Hence, while searching for geographical places in ancient Indian texts, this has to be taken into account. The Indian time is followed by the British, who adjusted it by 5 hours and 30 minutes to coincide with the local time of Greenwich. Thus, GMT was devised to harmonize with Indian standard time, which was midnight 1200 hrs. Thus, it was named as zero hour, since the day begins in India from that time. Hence, the European day starts at midnight. However, the nomenclature of weekdays is followed as per the Indian tradition.