Business: simple business date calculations in Ruby

We just open-sourced business, a simple library for doing business date calculations.

Usage

calendar = Business::Calendar.new(
  working_days: %w( mon tue wed thu fri ),
  holidays: ["01/01/2014", "03/01/2014"]
)

calendar.business_day?(Date.parse("Monday, 9 June 2014"))
# => true
calendar.business_day?(Date.parse("Sunday, 8 June 2014"))
# => false

date = Date.parse("Thursday, 12 June 2014")
calendar.add_business_days(date, 4).strftime("%A, %d %B %Y")
# => "Wednesday, 18 June 2014"
calendar.subtract_business_days(date, 4).strftime("%A, %d %B %Y")
# => "Friday, 06 June 2014"

date = Date.parse("Saturday, 14 June 2014")
calendar.business_days_between(date, date + 7)
# => 5

But other libraries already do this

Another gem, business_time, also exists for this purpose. We previously used business_time, but encountered several issues that prompted us to start business.

Firstly, business_time works by monkey-patching Date, Time, and FixNum. While this enables syntax like Time.now + 1.business_day, it means that all configuration has to be global. GoCardless handles payments across several geographies, so being able to work with multiple working-day calendars is essential for us. Business provides a simple Calendar class, that is initialized with a configuration that specifies which days of the week are considered to be working days, and which dates are holidays.

Secondly, business_time supports calculations on times as well as dates. For our purposes, date-based calculations are sufficient. Supporting time-based calculations as well makes the code significantly more complex. We chose to avoid this extra complexity by sticking solely to date-based mathematics.