Surya Siddhanta
सकृद् उद्गतम् अब्दार्धम् पश्यन्त्य् अर्कम् सुरासुराः। पितरः शशिगाः पक्षम् स्वदिनम् च नरा भुवि॥
The gods and demons behold the sun, after it is once risen, for half a year ; the ancestors (yitaras), who have their station in the moon, for a half-month (paksha) ; and men upon the earth, during their own day.
english translation