Surya Siddhanta
मन्दाद् अधः क्रमेण स्युश् चतुर्था दिवसाधिपाः। वर्षाधिपतयस् तद्वत् तृतीयाश् च प्रकीर्तिताः॥
Starting from Saturn downward, the fourth planet is called the regent of the day (divasadhipa) and the third planet is called the regent of the year (varshadhipati).
english translation