An almost perfect 247 year cycle is attributed to Rav Nachshon Gaon. Almost perfect… But not quite…

The series is based on שערים ללוח העברי by רחמים שר שלום הכהן.

A video of the author giving a shiur is at

The Google Translate version of the the text on the sefer’s page
https://www.machonso.org/mishol/item.asp?id=1898

In 5727, Rabbi Rahamim Sher-Shalom published the small and important book ‘The Basics of the Hebrew Calendar’, which concisely covered the basics of the Hebrew Calendar and brought great benefit to its users; but the expansion of the circle of those interested in the subject and the increase in the level of knowledge of many of them led the author, after 17 years, to compose his great book ‘Shearim to the Hebrew Calendar’ (Netanya 5744).

This book is unique in its appearance – an album edition (x3525 cm!), 235 pages, where each page includes one topic or sub-topic in the clear and precise handwriting of the author [!], including charts and tables – all ‘handmade’! 14 detailed pages in the book (hence its name) that include many chapters on the days of migration, the basics of the calendar (including appointments and postponements), the dates and their times, The day and its parts, the homelands, the periods, comparisons between the Hebrew calendar and the other calendars, and much more.

A complete picture of all the basic knowledge necessary to understand the various topics related to the Hebrew calendar, in clear and simple language, which meets the expectations of every ‘beginner’ – and also the requirements of an ‘advanced’ who wishes to deepen and expand his knowledge on this important subject, which includes a special combination of Torah and wisdom.

The author took into account that not all students of the book want to delve deeper into the set of topics, and therefore included on the second page of each cover a summary of the material presented in the chapter, while in the body of the chapter the topics are presented in detail.

A revised and expanded new edition from 5769. The new edition that came out after 25 years is based on the good old one, with the addition of new pages and parts of pages written this time in printed letters (which highlights throughout the book the additions and changes in the new edition).

The importance of the book ‘Gates to the Hebrew Calendar’ and its usefulness to the learner, researcher and anyone interested in the Jewish calendar cannot be overstated. This is a treasure that deserves to be found in every home.