Astrology is the study of how we evolve through time. So here is a ‘definitions’ post on how we measure time in the Vedic system. We call our calendar Panchangam.
The zodiac is made of 360 degrees. We measure the arc of a circle in – degrees, minutes, seconds. Vedic astrology/astronomy follows the true zodiac in which we calculate the precession/wobbling/tilt of the poles/earth. This correction is called Ayanamsha. So Vedic mathematics is extremely accurate.
First the year/Samvatsara. There is a cycle of 60 years each of them have names. This 60 yrs is the nearest possible for 5 cycles of Jupiter transit + 2 cycles of Saturn transit to coincide. (Their cycles coincide at 60yrs, as Jupiter takes 12 yrs to travel around the zodiac and Saturn takes 30 yrs.) A Vedic year finishes when both Moon and Sun are together in the same degree in Meen/Pisces. The day after this, is the start of the new year.
Now there are two movements/Ayan of the Sun in this year. The apparent south ward movement of the Sun /Dakshinayan and the Uttarayan/North ward movement of the Sun. These are caused by the precession/tilt of the axis of the earth. The Uttarayan period of 6 months is generally considered more auspicious for any activity.
There are 12 months/Maas in a year, they have different names from Chaitra, Vaishakh, Jeyshta, Ashadh, Shravan, Bhadrapad, Ashwin, Kartik, Margashirsh, Paush, Magh, Phalgun. Each of these end when the Sun and moon are together in a sign, i.e. they end on a no moon day/amavasya. We use both the solar year and the lunar year (luni-solar system) and the discrepancy between the two is adjusted every three years where a 13th month is added to the year. This 13th month is called the ‘Adhik maas’/extra month and is very good period for doing pujas and stuff.
(Solar month/Saur maas is when the Sun enters into a sign of the zodiac and then exits it. This day when it transits, is called the Sankranti (good forceful forward movement). Sankranti is generally on the 15th of every month when the Sun changes his sign.
The lunar month/Chandra maas is from one Amavasya/no moon day to the next. Those families who follow the strict rules related to time use this Lunar month for their day to day activities. When I use ‘day’, I mean lunar-day always.)
There are 6 seasons/Rutu in India. 2 months make up one season. Starting with Vasant/spring, Grishma/summer, Varsha/rains, Sharad/pleasant weather, Hemant/pre-winter, Shishir/winter.
Now the fortnights, the dark fortnight of the waning moon/Krishna paksha, and the bright fortnight of the waxing moon/Shukla paksha. (Depending on which sort of ritual you are performing, you choose the time. For rituals which are to bring increase , choose the shukla paksha And for rituals which intend decrease of something use the Krishna paksha period.)
Now the day/Vaar. The day starts with sunrise (not midnight) in Indian panchangams/calendars. There are 7 days, from Ravivar/Sunday, Somvar, Mangalvar, Budhavar, Guruvar, Shukravar to Shanivar/Saturday.
Now one Lunar day in context of the movement of the Sun and the Moon is called a Tithi, When the moon completes 12 arc degrees of its movement with reference to the Sun, it is a Tithi/ Hindu lunar day. There are fourteen tithis in each fortnight, then one Amavasya/no moon and one Purnima/Full Moon in each month. Thus there are 30 tithis in a lunar month. (The starting and ending of a Tithi depends upon the degree of the Moon from that of the Sun. Thus a Tithi can start or end at any time in a day.)
Now the half lunar day is called a Karan. Karan is ½ of the Moon Phase day/Tithi and have different names. One Karan period is when the Moon travels 6 degrees arc in reference to the Sun. There are four types of Fixed Karanas as they occur once in a month. And there are seven types of recurring Karans and they each repeat eight times during the lunar month.
Then Yog. There are 27 types of Yog in a sequence from Vishakhamba to Vaidhriti. This is another mathematical calculation, the degrees of the Sun and the Moon in the sky are added then divided by 13°20′. The Yog are in a sequence, so if the quotient is 1 and the remainder is 2deg 3 sec it means that the 1st Yog Vishakhamba has elapsed and the 2nd yog in sequence Priti is on.
The Nakshatra of the day is the one in which the Moon is in during the Sunrise. There are 27 Nakshatra/Lunar mansions each of 13 arc degrees 20 seconds in width. (The moon takes approx 28 days to cover the entire zodiac so an extra small nakshatra arc named ‘Abhijit’ is used as a correction factor. It has spiritual implications in Jyotish.)
The current Rashi/zodiac sign is the one which is occupied by the Moon at sunrise. There are 12 signs and the Moon takes about 2.25 days to transit one sign.
(Your software, even the phone app mentions these details for the day if you want to know)
So, for pujas/rituals or for telling someone my birth day in the Vedic system, I will tell the day as per the Panchangam, I will use the names of the Tithi/Lunar day, Paksha/fortnight, Maas/month and Samvatsara/year to define it.
The most basic are 5 (panch) components (angam), of time, Panchangam.
1. Day of Week/ Vaar
2. Nakshatra (Lunar mansion in which Moon is transiting)
3. Tithi (moon phase)
4. Karana (half a lunar day)
5. Yoga (a calculation for the distance separating the Sun and Moon)
As per Vedic Astrology, it is required to say out aloud the name of these 5 elements in the morning.
• Saying the Vaara (Day of the Week) will help enjoy longevity
• Saying the Nakshatra (Lunar mansion the Moon is in) will help dissolve karmas
• Saying the Tithi (Moon Phase name) will help one enjoy prosperity
• Saying the Yoga will help in keeping miseries away
• Saying the Karan will help in getting desires fulfilled.
This was the very basic stuff taught to me as a child. For astrologers, ‘time’ is a function of the movements of the Sun and the Moon.