The Tamil calendar (Tamil: தமிழ் நாட்காட்டி) is a solar calendar used across Tamil Nadu, Sri Lanka, and Tamil communities worldwide for religious observances, muhurtham selection, and cultural festivals. Unlike the Gregorian calendar, which divides the year into months of fixed lengths, the Tamil calendar divides the year by the Sun's actual passage through the 12 zodiac signs — making each month's length slightly variable, typically 29 to 32 days.
The Rasi & Rise engine uses the Tamil calendar natively: when you search for auspicious dates, the results display the Tamil month and date alongside the Gregorian date, so you can verify against a traditional panchangam.
The Solar Year — Chithirai to Panguni
The Tamil new year begins with Chithirai (சித்திரை), which starts when the Sun enters the sidereal sign of Aries (Mesha Rasi) — typically around April 14 in the Gregorian calendar. The year ends with Panguni (பங்குனி), after which the cycle restarts. The table below shows all 12 months with approximate Gregorian spans.
| # | Tamil Month | Transliteration | Approximate Gregorian Span |
|---|---|---|---|
| 1 | சித்திரை | Chithirai | Apr 14 – May 14 |
| 2 | வைகாசி | Vaikasi | May 15 – Jun 14 |
| 3 | ஆனி | Aani | Jun 15 – Jul 16 |
| 4 | ஆடி | Aadi | Jul 17 – Aug 16 |
| 5 | ஆவணி | Aavani | Aug 17 – Sep 16 |
| 6 | புரட்டாசி | Purattasi | Sep 17 – Oct 17 |
| 7 | ஐப்பசி | Aippasi | Oct 18 – Nov 15 |
| 8 | கார்த்திகை | Karthigai | Nov 16 – Dec 15 |
| 9 | மார்கழி | Margazhi | Dec 16 – Jan 13 |
| 10 | தை | Thai | Jan 14 – Feb 12 |
| 11 | மாசி | Masi | Feb 13 – Mar 14 |
| 12 | பங்குனி | Panguni | Mar 15 – Apr 13 |
Spans are approximate and shift slightly from year to year based on the Sun's actual position. The exact start date of each month is determined by the moment the Sun crosses the sidereal sign boundary.
Why Tamil Dates Differ from Western Calendars
The core difference is sidereal vs. tropical astronomy. The Gregorian calendar is based on the tropical year — the time from one vernal equinox to the next — which defines the seasons. The Tamil calendar is based on the sidereal year — the time it takes the Sun to return to the same position relative to the fixed stars. Because of a slow wobble in Earth's axis called the precession of the equinoxes, the sidereal year is about 20 minutes longer than the tropical year. Over centuries, this causes the Tamil calendar's month starts to drift about 23 days later than the equinox-anchored Gregorian dates might suggest.
This also explains why Tamil Vedic astrology uses sidereal zodiac signs (called Rasis) rather than tropical signs. When the Rasi & Rise engine calculates your Moon sign or your birth nakshatra, it uses sidereal longitudes — placing the Sun in Aries only once it has physically crossed into the sidereal Aries constellation, not at the tropical spring equinox.
In practical terms: a person born on April 5 in the Gregorian calendar falls in the Tamil month of Panguni (the last month), not Chithirai — because the Tamil new year has not yet begun. This surprises many people who are used to Western sun-sign astrology placing early April firmly in "Aries season."
The 60-Year Cycle
The Tamil calendar also tracks a repeating 60-year cycle (Shashti Abda Poorti), in which each year carries a unique name. The current cycle includes years such as Paraabhava and Pilavanga — names drawn from a list that has been in continuous use for over two millennia. When someone reaches their 60th birthday, it is celebrated as a major milestone because they have completed exactly one full cycle. The 60-year names cycle through themes of prosperity, challenge, and transformation, and traditional almanacs note each year's name prominently alongside the month and tithi.
How the Tamil Calendar Drives Muhurtham
Every auspicious date search on Rasi & Rise is grounded in the Tamil calendar. The engine identifies the active Tamil month, the lunar tithi, the nakshatra, the yogam, and the karanam for each candidate window. Certain Tamil months carry traditional associations — Aadi and Thai are considered strong months for auspicious events in many families, while Aippasi and Margazhi are more often avoided for weddings. The engine factors these month-level preferences into its scoring when you use the date finder.