A very useful survey by Svante Janson appeared recently: The Icelandic calendar. Scripta Islandica, Isländska Sällskapets årsbok 62/2011, Uppsala 2011, pp. 51-104. He already notices the coincidence between Jewish Second Temple period 364DY [DY = days per year] calendars and the Icelandic one, whereas he knows the former mostly by VanderKam's summarising book. Indeed, the Qumranic calendars including those of the Book of Jubilees and 1Enoch are too distinct from the Icelandic one. There is more appropriate Jewish material, however.( Read more... )