Tibetan Calendar Mathematics

Svante Janson is a mathematician at Uppsala University, and this paper is his detailed scholarly analysis of the calculations underlying the Tibetan calendar, translating the traditional computational rules into modern mathematical notation. Its strength is that it works directly from the calendar's own astronomical and arithmetic rules rather than from secondhand description, making the actual mechanics of a genuinely complex lunisolar system checkable and explicit. Its limit is that it is a technical mathematical paper aimed at readers wanting the calculation method itself, not an introduction to the calendar's religious significance, so a claim about that religious meaning needs a source focused on that side of the calendar.