Bhagavatapurana 9.6.37

9.6.37

yāvat sūrya udeti sma yāvac ca pratitiṣṭhati /
tat sarvaṃ yauvanāśvasya māndhātuḥ kṣetramucyate //

37. From the point from which the sun starts to the point where he stops (breaks his journey), all that under the sun is called the land of Mandhatri, son of Yuvanasva.