Module: IB::BuisinesDays

Defined in:
lib/ib/eod.rb

Class Method Summary collapse

Class Method Details

.business_days_between(start_date, end_date) ⇒ Fixnum

Calculates the number of business days in range (start_date, end_date]

Parameters:

  • start_date (Date)
  • end_date (Date)

Returns:

  • (Fixnum) 


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# File 'lib/ib/eod.rb', line 12

def self.business_days_between(start_date, end_date)
  days_between = (end_date - start_date).to_i
  return 0 unless days_between > 0

  # Assuming we need to calculate days from 9th to 25th, 10-23 are covered
  # by whole weeks, and 24-25 are extra days.
  #
  # Su Mo Tu We Th Fr Sa    # Su Mo Tu We Th Fr Sa
  #        1  2  3  4  5    #        1  2  3  4  5
  #  6  7  8  9 10 11 12    #  6  7  8  9 ww ww ww
  # 13 14 15 16 17 18 19    # ww ww ww ww ww ww ww
  # 20 21 22 23 24 25 26    # ww ww ww ww ed ed 26
  # 27 28 29 30 31          # 27 28 29 30 31
  whole_weeks, extra_days = days_between.divmod(7)

  unless extra_days.zero?
    # Extra days start from the week day next to start_day,
    # and end on end_date's week date. The position of the
    # start date in a week can be either before (the left calendar)
    # or after (the right one) the end date.
    #
    # Su Mo Tu We Th Fr Sa    # Su Mo Tu We Th Fr Sa
    #        1  2  3  4  5    #        1  2  3  4  5
    #  6  7  8  9 10 11 12    #  6  7  8  9 10 11 12
    # ## ## ## ## 17 18 19    # 13 14 15 16 ## ## ##
    # 20 21 22 23 24 25 26    # ## 21 22 23 24 25 26
    # 27 28 29 30 31          # 27 28 29 30 31
    #
    # If some of the extra_days fall on a weekend, they need to be subtracted.
    # In the first case only corner days can be days off,
    # and in the second case there are indeed two such days.
    extra_days -= if start_date.tomorrow.wday <= end_date.wday
                    [start_date.tomorrow.sunday?, end_date.saturday?].count(true)
                  else
                    2
                  end
  end

  (whole_weeks * 5) + extra_days
end