The six Ruthus
| Ruthu | Tamil months | 2029 Start |
|---|---|---|
| Ilavenil (spring) Vasantha Ruthu | Chithirai, Vaikasi | 14 April 2029, 1:30 AM |
| Muthuvenil (summer) Grishma Ruthu | Aani, Aadi | 15 June 2029, 4:58 AM |
| Kaar (rainy season) Varsha Ruthu | Avani, Purattasi | 17 August 2029, 12:12 AM |
| Koothir (autumn) Sarath Ruthu | Aippasi, Karthigai | 17 October 2029, 12:01 PM |
| Munpani (early winter) Hemantha Ruthu | Margazhi, Thai | 16 December 2029, 2:26 AM |
| Pinpani (late winter) Sisira Ruthu | Maasi, Panguni | 12 February 2029, 8:05 PM |
Equinoxes and solstices
| Event | Time | Day length |
|---|---|---|
| March equinox | 20 March 2029, 11:01 AM | 12:07 hours |
| June solstice | 21 June 2029, 4:48 AM | 13:47 hours |
| September equinox | 22 September 2029, 8:37 PM | 12:08 hours |
| December solstice | 21 December 2029, 5:14 PM | 10:30 hours |
Ayanam
- Uttarayanam
- 14 January 2029, 7:03 AM
- Dakshinayanam
- 16 July 2029, 3:49 PM
How it is calculated
Each Ruthu is two Tamil months. A new Ruthu begins when the Sun enters Mesham, Mithunam, Simmam, Thulam, Dhanusu or Kumbam.
At an equinox, day and night are nearly equal. At the June solstice the day is longest in India; in December it is shortest. These are astronomical (Sayana) figures.
In the panchangam, Uttarayanam begins on Thai 1 and Dakshinayanam begins on Aadi 1.