Book of Enoch (1 Enoch) 82:4

Blessed are all the righteous, blessed are all those who walk in the way of righteousness and sin not as the sinners, in the reckoning of all their days in which the sun traverses the heaven, entering into and departing from the portals for thirty days with the heads of thousands of the order of the stars, together with the four which are intercalated which divide the four portions of the year, which lead them and enter with them four days.

Background and history of Book of Enoch (1 Enoch), and issues with this book.