For whatever it’s worth, here is a query that contains a (very) long rule which:
- expects two dates in the form
YYYYMMDD - returns true only if they are on the same day of the week
#+BEGIN_QUERY
{
:title [:b "sameWeekDay"]
:inputs [:today]
:rules [
[(sameWeekDay ?date-a ?date-b)
[(mod ?date-a 100) ?monthday-a]
[(mod ?date-a 10000) ?mod-a]
[(quot ?mod-a 100) ?month-a]
[(- ?month-a 8) ?month8-a]
[(quot ?month8-a 6) ?month6-a]
[(* ?month6-a 12) ?month12-a]
[(- ?month-a ?month12-a) ?monthnum-a]
[(inc ?monthnum-a) ?monthinc-a]
[(* 13 ?monthinc-a) ?month13-a]
[(quot ?month13-a 5) ?month5-a]
[(quot ?date-a 10000) ?year-a]
[(+ ?year-a ?month6-a) ?year6-a]
[(mod ?year6-a 100) ?yearnum-a]
[(quot ?yearnum-a 4) ?year4-a]
[(quot ?year6-a 100) ?century-a]
[(quot ?century-a 4) ?century4-a]
[(* 5 ?century-a) ?century5-a]
[(+ ?monthday-a ?month5-a ?yearnum-a ?year4-a ?century4-a ?century5-a) ?sum-a]
[(mod ?sum-a 7) ?d-a]
[(mod ?date-b 100) ?monthday-b]
[(mod ?date-b 10000) ?mod-b]
[(quot ?mod-b 100) ?month-b]
[(- ?month-b 8) ?month8-b]
[(quot ?month8-b 6) ?month6-b]
[(* ?month6-b 12) ?month12-b]
[(- ?month-b ?month12-b) ?monthnum-b]
[(inc ?monthnum-b) ?monthinc-b]
[(* 13 ?monthinc-b) ?month13-b]
[(quot ?month13-b 5) ?month5-b]
[(quot ?date-b 10000) ?year-b]
[(+ ?year-b ?month6-b) ?year6-b]
[(mod ?year6-b 100) ?yearnum-b]
[(quot ?yearnum-b 4) ?year4-b]
[(quot ?year6-b 100) ?century-b]
[(quot ?century-b 4) ?century4-b]
[(* 5 ?century-b) ?century5-b]
[(+ ?monthday-b ?month5-b ?yearnum-b ?year4-b ?century4-b ?century5-b) ?sum-b]
[(mod ?sum-b 7) ?d-b]
[(= ?d-a ?d-b)]
]
]
:query [
:find ?today
:in $ ?today %
:where
(sameWeekDay ?today 20230806)
]
}
#+END_QUERY