Tamil Calendar: How It Works
The Tamil calendar is solar: months begin when the sun enters a new zodiacal sign, so dates align closely with the Gregorian calendar while the month boundaries fall mid-month rather than on the first.
The twelve months
| Tamil month | Approximate Gregorian |
|---|---|
| Chithirai (சித்திரை) | Mid-April to mid-May |
| Vaikasi (வைகாசி) | Mid-May to mid-June |
| Aani (ஆனி) | Mid-June to mid-July |
| Aadi (ஆடி) | Mid-July to mid-August |
| Aavani (ஆவணி) | Mid-August to mid-September |
| Purattasi (புரட்டாசி) | Mid-September to mid-October |
| Aippasi (ஐப்பசி) | Mid-October to mid-November |
| Karthigai (கார்த்திகை) | Mid-November to mid-December |
| Margazhi (மார்கழி) | Mid-December to mid-January |
| Thai (தை) | Mid-January to mid-February |
| Maasi (மாசி) | Mid-February to mid-March |
| Panguni (பங்குனி) | Mid-March to mid-April |
Month lengths vary between 29 and 32 days, because the Earth moves at different speeds through its elliptical orbit — the sun spends longer in some zodiacal signs than others. This is a genuine astronomical variation rather than a calendrical convention.
Solar, not lunar
Because the calendar tracks the sun, Tamil New Year falls on roughly the same Gregorian date each year — around 14 April. Lunar calendars, by contrast, drift by about eleven days a year against the Gregorian, which is why some Indian festivals move substantially and Tamil month boundaries do not.
Some observances within the Tamil tradition are nevertheless calculated using lunar positions or nakshatras, which is why a few festival dates still shift.
The sixty-year cycle
Years are named rather than only numbered, cycling through sixty names — Prabhava, Vibhava, Sukla, and so on — before repeating. The cycle is shared with several other Indian calendars and appears on traditional almanacs and in temple inscriptions, which is how many undated inscriptions are placed within a sixty-year window.
Major observances
| Festival | When |
|---|---|
| Puthandu (Tamil New Year) | First day of Chithirai, around 14 April |
| Pongal | First day of Thai, around 14 January — the harvest festival |
| Aadi Perukku | 18th day of Aadi, marking the river's rise |
| Karthigai Deepam | Karthigai, on the full moon |
| Margazhi | The whole month, observed for devotional music and early-morning ritual |
Panchangam
Traditional almanacs list five elements for each day — tithi (lunar day), vaara (weekday), nakshatra (lunar mansion), yoga and karana. These determine auspicious and inauspicious periods used for scheduling weddings, housewarmings and other significant events, and they require lunar as well as solar calculation.
Calendar conversions here are calculated from standard astronomical rules. Regional traditions differ in their conventions, and for religious or ceremonial timing you should follow the panchangam your community observes rather than a general converter.