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,
Vṛṣabha the Tamil Hindu calendar. The ancient and medieval era Sanskrit texts of India vary in their calculations about the duration of Vrsabha, just like they do with other months. For example, the "Surya Siddhanta" calculates the duration of Vrishabha to be 31 days, 10 hours, 5 minutes and 12 seconds. In contrast, the "Arya Siddhanta" calculates the duration of Vrsabha to be 31 days, 9 hours, 37 minutes and 36 seconds. The Indian solar month names are significant in epigraphical studies of South Asia. For example, "Vrsabha" month, along with other solar months, are found inscribed in medieval era Hindu