rebol [ Library: [ level: 'beginner platform: 'all type: [tool function] domain: [math financial] tested-under: [windows bsd linux] support: none license: [mit] ] file: %work-days.r date: 18-feb-2007 author: "Sunanda" version: 0.0.1 title: "Calculate working days between two dates" purpose: {Given two dates, and a list of holidays that occur between them, returns the number of work days between those two days. With the /non refinement, will return the number of non-working days between the two dates.} ] calc-work-days: func [ date1 [date!] date2 [date!] holidays [block!] /non /local dates offset hol-count working-days ] [ ;; Put dates in order ;; ------------------ dates: copy reduce [date1] either date1 < date2 [append dates date2] [insert dates date2] ;; count holidays in range ;; ----------------------- hol-count: 0 foreach hd holidays [ if all [ hd/weekday <= 5 ;; got to be a weekday to count hd >= dates/1 hd <= dates/2] [ hol-count: hol-count + 1 ] ] ;; Round dates to Mondays ;; ---------------------- offset: 0 offset: offset + pick [0 -1 -2 -3 -4 -4 -4] dates/1/weekday dates/1: dates/1 + 1 - dates/1/weekday offset: offset + pick [-5 -4 -3 -2 -1 -1 -1] dates/2/weekday dates/2: dates/2 + 8 - dates/2/weekday ;; Calculate the working / non-working days ;; ---------------------------------------- working-days: (dates/2 - dates/1) / 7 * 5 + offset - hol-count if non [return (abs (date1 - date2)) - working-days] return working-days ]