Book of Enoch (1 Enoch) 72:9
And during this period the day becomes daily longer and the night nightly shorter to the thirtieth morning.
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.