Adding Days to a Date but Excluding Weekends

Question

Given a date how can I add a number of days to it, but exclude weekends. For example, given 11/12/2008 (Wednesday) and adding five will result in 11/19/2008 (Wednesday) rath

Answer 1

F# flavor of http://stackoverflow.com/questions/1044688 's answer:

namespace FSharpBasics

module BusinessDays =

    open System;

    let private weekLength = 5

    (*operation*)
    let addBusinessDays (numberOfBusinessDays: int) (startDate: DateTime) =
        let startWeekDay = startDate.DayOfWeek
        let sign = Math.Sign(numberOfBusinessDays) 
        let weekendSlide, businessDaysSlide = 
            match startWeekDay with
            | DayOfWeek.Saturday when sign > 0 -> (2, -1)
            | DayOfWeek.Saturday when sign < 0 -> (-1, 1)   
            | DayOfWeek.Sunday when sign > 0 -> (1, -1)
            | DayOfWeek.Sunday when sign < 0 -> (-2, 1)
            | _ -> (0, 0)
        let baseStartDate = startDate.AddDays (float weekendSlide)        
        let days = Math.Abs (numberOfBusinessDays + businessDaysSlide) % weekLength
        let weeks = Math.Abs (numberOfBusinessDays + businessDaysSlide) / weekLength
        let baseWeekDay = int baseStartDate.DayOfWeek
        let oneMoreWeekend =
            if sign = 1 && days + baseWeekDay > 5 || sign = -1 && days >= baseWeekDay then 2
            else 0
        let totalDays = (weeks * 7) + days + oneMoreWeekend
        baseStartDate.AddDays (float totalDays)

    []
    let main argv =
        let now = DateTime.Now 
        printfn "Now is %A" now
        printfn "13 business days from now would be %A" (addBusinessDays 13 now)
        System.Console.ReadLine() |> ignore
        0