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4.2.1 Calendar Functions

Included in the combine package are two Guile modules to work with dates from a number of calendars, both obscure and common. The basis for them is the set of calendar functions that are shipped with Emacs.

The reason that these functions deserve special notice here is that date comparisons are a common type of comparison that often cannot be made directly on a character string. For example I might have trouble knowing if "20030922" is the same date as "22 September 2003" if I compared strings; however, comparing them as dates allows me to find a match. We can even compare between calendars, ensuring that "1 Tishri 5764" is recognized as the same date as "20030927".

The calendar module can be invoked as (use-modules (combine_scm calendar)). It provides functions for converting from a variety of calendars to and from and absolute date count, whose 0-day is the imaginary date 31 December 1 B.C. In the functions, the absolute date is treated as a single number, and the dates are lists of numbers in (month day year) format unless otherwise specified.

The calendar functions are as follow:


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