The described function (WEEKNUM) does not support the Persian calendar, which is main official calendar in Iran and Afghanistan.
Extend the function so that it supports the Persian calendar.
Part 4, 3.17.7.342
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Proposed Disposition of DIS 29500 Comment IR-0005 (Modified: 2008-01-02) We agree that the WEEKNUM function does not support the Persian calendar date base, but we are not aware of an accepted international standard for the Persian calendar to reference. Instead w W e believe the best approach is to remain based on the ISO 8601 date base . , but also provide the following change to Part 4, ยง3.17.7.342, page 2,819, after line 23, to show how the Persian calendar could be used with this design: [Note: To use this function with another calendar system, the following approach is recommended: =WEEKNUM(DateInQuestion-FirstDayOfYearForDateInQuestion) where DateInQuestion and FirstDayOfYearForDateInQuestion are in the ISO 8601 date base. end Note]
