Surya Siddhanta
अतस् तत्र दिनम् त्रिम्शन्नाडिकम् शर्वदी तथा । हानिवृद्धी सदा वामम् सुरासुरविभागयोः॥
Hence, in the latter situation, the day is of thirty nadis, and the night likewise : in the two hemispheres of the gods and demons there take place a deficiency and an excess, always opposed to one another.
english translation