The Universal System of Astronomy, Part Two

...regarding the rains and other seasons. One might ask: how can there be a fixed understanding of these seasons given the lack of uniform signs? The signs of the seasons ṛtu-chihna; the physical indicators like blooming flowers or weather patterns that define a season, such as those for Spring Vasanta, are established based on the specific characteristics of each country. Because these signs are perceived differently from region to region, they are based on local observation, tradition, and the repeated association of various natural phenomena in the world.

Therefore, because there are no "universal" seasonal signs that apply to every country, one might think that regional observations are contradictory or confused. The essence of the argument here is to prevent such confusion when observing the different markers of time across various lands. verse 97

An objection is raised: "If that is the case, then why did Bhāskara Bhāskarācārya, the 12th-century mathematician and astronomer and others describe these signs in works such as the Siddhānta Shiromaṇi The "Crown of Treatises"; a foundational text of Indian astronomy written in 1150 CE?"

In response, the following verses describe the fresh sprouts of the Mango tree sahakara; the fragrant mango tree, often used as a symbol of spring, the gathering of dark clouds, and the abundance of golden flowers:

Signs of trees and nature were described by Bhāskara and the learned scholars who preceded him specifically as they appear in the Middle Country Madhyadeśa; the central region of the Indo-Gangetic plain, considered the cultural and scientific heart of ancient India. They described the sequence of the seasons—starting with Spring—according to how they are observed there. The previous verses describing these signs should be understood in this context. For example, the appearance of new sprouts marks Spring original: vasantādi, while the approach of dark, water-laden clouds occurs when the seasons transition toward the monsoon.