Book of Enoch (1 Enoch) 72:15
And the sun mounts up to make the day shorter and the night longer, and the sun returns to the east and enters into the sixth portal, and rises from it and sets thirty mornings.
Background and history of Book of Enoch (1 Enoch), and issues with this book.
R. H. Charles, The Book of Enoch (London: SPCK, 1917), public domain. The verse text is the English Wikisource transcription of that translation. Charles’s editorial signs are kept. He rearranges some verses in chapters 5, 39, 90, 91, and 106, so those chapters are not a straight 1, 2, 3 sequence.