The six Ruthus
| Ruthu | Tamil months | 2028 Start |
|---|---|---|
| Ilavenil (spring) Vasantha Ruthu | Chithirai, Vaikasi | 13 April 2028, 9:51 PM |
| Muthuvenil (summer) Grishma Ruthu | Aani, Aadi | 15 June 2028, 1:20 AM |
| Kaar (rainy season) Varsha Ruthu | Avani, Purattasi | 16 August 2028, 8:35 PM |
| Koothir (autumn) Sarath Ruthu | Aippasi, Karthigai | 17 October 2028, 8:22 AM |
| Munpani (early winter) Hemantha Ruthu | Margazhi, Thai | 15 December 2028, 10:47 PM |
| Pinpani (late winter) Sisira Ruthu | Maasi, Panguni | 13 February 2028, 4:29 PM |
Equinoxes and solstices
| Event | Time | Day length |
|---|---|---|
| March equinox | 20 March 2028, 7:47 AM | 12:07 hours |
| June solstice | 21 June 2028, 1:31 AM | 12:45 hours |
| September equinox | 22 September 2028, 5:15 PM | 12:07 hours |
| December solstice | 21 December 2028, 1:50 PM | 11:30 hours |
Ayanam
- Uttarayanam
- 15 January 2028, 3:30 AM
- Dakshinayanam
- 16 July 2028, 12:13 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.