Lanka and Mauritius. Tropical vernal equinox fall around 22 March, and by adding 23 degrees of trepidation (oscillation) to it, we get the Hindu sidereal or Nirayana Mesha Sankranti (Sun's transition into nirayana Aries). Hence, the Tamil calendar begins on the same date in April which is observed by most traditional calendars of the rest of India – Assam, Bengal, Kerala, Odisha, Manipur, Punjab etc. This also coincides with the traditional new year in Burma, Cambodia, Laos, Sri Lanka, Bangladesh, Nepal, and Thailand. Week The days of week (Kiḻamai) in the Tamil Calendar relate to the celestial bodies in the solar system: Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn, in that order. The week starts with Sunday. Months The number of days in a month varies between 29 and 33. These are the months of the Tamil Calendar. The Sanskrit month starts a few weeks ahead of the Tamil month, since the Tamil calendar is a solar calendar, while the Sanskrit calendar is a lunisolar calendar. Seasons The Tamil year, in keeping with the old Indic calendar, is divided into six seasons, each of which lasts two months: Sixty-year cycle The 60-year cycle is common to both North and South Indian traditional calendars, with the same name and sequence of years. Its earliest reference is to be found in Surya Siddhanta, which Varahamihirar (550 CE) believed to be the most accurate of the then current theories of astronomy. However, in the Surya Siddhantic list, the first year was Vijaya and not Prabhava as currently used. There are some parallels in this sexagenary cycle with the Chinese calendar. The Surya Siddhanta and other Indian classical texts on astronomy had some influence on the Chinese calendar although it merits attention that the sexagenary cycle in China is itself very old. After the completion of sixty years, the calendar starts a new with the first year. This corresponds to the Hindu "century." The Vakya or Tirukannitha Panchangam (the traditional Tamil almanac) outlines this sequence. It is related to the position of the planets in the sky with respect to earth. It means that the two major planets Sani/Saturn (which takes 30 years to complete one cycle round the sun) and the Viyaḻan/Jupiter (which takes 12 years to complete one cycle round the Sun) comes to the same position after 60 years. The following list presents the current 60-year cycle of the Tamil