Reflecting upon the characteristics of time and place, one should according to his inclinations observe, after proper search, vows and rules about fasts.
आहारनियमं चैव देशे काले च सात्त्विकम्। तत् परीक्ष्यानुवर्तेत तत्प्रवृत्त्यनुपूर्वकम्॥