Lunar day around the Sun at the same time, the Moon must travel further to return to the same phase. On average, this synodic period lasts 29 days, 12 hours, 44 minutes, and 3 seconds. This is the mean figure since the speed of the Earth–Moon system around the Sun varies slightly during a year due to the eccentricity of its elliptical orbit, variances in orbital velocity, and a number of other periodic and evolving variations about its observed, relative, mean values, which are influenced by the gravitational perturbations of the Sun and other bodies in the Solar System. As a result,
Siṃha month of Karkaṭa, and followed by the solar month of Kanyā. The Simha month is called "Avani" in the Tamil Hindu calendar. The ancient and medieval era Sanskrit texts of India vary in their calculations about the duration of Simha, just like they do with other months. For example, the "Surya Siddhanta", dated to c. 400 CE, calculates the duration of Simha to be 31 days, 0 hours, 26 minutes and 48 seconds. In contrast, the "Arya Siddhanta" calculates the duration of the Simha month to be 31 days, 2 hours, 5 minutes and 31 seconds. The Indian solar month