Learn
Fourteen short lessons, from what a jathagam is to reading one on this site.
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Each has a picture, a link into the tool it explains and three questions to check yourself. Below them, pages that answer one question at a time.
The fourteen lessons
In order. Each one ends in the tool it explains.
- 1.What a jathagam is, and what you need to cast one
A horoscope is a picture of the sky at the moment you were born, seen from the place you were born.
- 2.The twelve rasis
Twelve signs of thirty degrees each, every one with a ruling graha and a character of its own.
- 3.The 27 nakshatras and their padas
The same circle cut finer: twenty-seven stars of 13°20′, each in four quarters.
- 4.The nine grahas and what each stands for
Seven planets you can see and two points you cannot, each carrying a set of life’s matters.
- 5.The lagna and the twelve houses
The rising sign becomes the first house, and every area of life is counted from it.
- 6.The panchangam’s five limbs, and how a Tamil day is read
Tithi, vara, nakshatra, yoga and karana: five facts about the day, all read at sunrise.
- 7.Good and bad hours: Rahu kaal, Gowri and Nalla neram
The daylight is cut into equal parts, and each weekday gives certain parts to certain names.
- 8.The Vimshottari dasha, and how to read "running Budhan"
A life divided into nine planetary periods, started by the birth star and laid end to end.
- 9.Transits, and Sade sati in plain words
Where the planets are today, counted from your birth Moon.
- 10.Porutham: what the ten matches check
Ten comparisons of two birth stars, each graded full, partial or none.
- 11.Doshams, without fear: Sevvai and Kala sarpa
What the two doshams families ask about actually are, how often they occur, and what cancels them.
- 12.Muhurtham: how a date is chosen
A good day is built up from the month, the weekday, the tithi, the star and the rising sign.
- 13.Vargas, and why the navamsa matters
Each sign cut into smaller parts, and each set of parts read as a chart of its own.
- 14.How to read this app’s jathagam page, top to bottom
A map of the page, in the order it is printed, with what to look at first on each sheet.
Every word the lessons use is also in the glossary, 447 terms with a line each.
The calendar
Why two almanacs can print different dates for one day, and which rule produced each.
- Why two Tamil calendars disagree about the date
Your wall calendar and an astronomical one can put the first of a Tamil month on different days, and both are right by their own rule.
6 min · updated 2026-09-26
- Why this sunrise differs from the one in the newspaper
Two reasons: which part of the Sun counts as risen, and the fact that one printed time has to cover a whole state.
5 min · updated 2026-09-26
- Why Deepavali falls on different days north and south
The two halves of the country are keeping two different observances on two adjacent tithis, not one festival that cannot agree with itself.
5 min · updated 2026-09-26
- How a festival date is fixed
A tithi rarely fills a whole day, so every festival also names the instant at which its tithi has to be running.
6 min · updated 2026-09-26
The day
The windows a household plans around, and where they come from.
- What Rahu kaal is, and what it is not
One eighth of the daylight on a fixed weekday rota, which is why it moves through the year and is never the same in two towns.
5 min · updated 2026-09-26
The chart
What a horoscope is made of, and what each part is held to mean.
- Why your Western sign differs from your rasi
The two zodiacs count from different starting points. The angle between them is the ayanamsa, about 24 degrees now, and it moves most birthdays back a sign.
5 min · updated 2026-09-26
- Why your Tamil birth star may differ
Two calculators can give you two different nakshatras: the Moon crossed a boundary that day, or the two used different ayanamsas. Here is how to tell which.
6 min · updated 2026-09-26
- What sade sati is, and is not
Saturn crossing the three signs around your natal Moon, and the difference between a date that can be checked and a meaning that is a tradition.
6 min · updated 2026-09-26
- What a dasha is
Vimshottari divides 120 years among nine grahas and starts from the Moon at birth, which is why a few minutes of birth time move every date in the table.
6 min · updated 2026-09-26
Occasions
Choosing a day, and keeping one.
- Why shraddha is not the date of death
The yearly thivasam is kept on the tithi in its own lunar month, not the English anniversary, so it moves by weeks — and a leap-month year offers two.
6 min · updated 2026-09-26
- What the ten poruthams measure
The ten Tamil marriage poruthams named one by one, what each of them actually compares, and what a count out of ten is and is not evidence of.
6 min · updated 2026-09-26
- How a wedding date is chosen
The order a Tamil muhurtham is worked out in: what is ruled out wholesale, what the day itself decides, and why two astrologers hand a family different lists.
6 min · updated 2026-09-26