Counting, adding or subtracting business days in R

Calculating the number of days between two dates in R is as simple as using + or -. However, if you only want to count the business days (e.g. in a B2B context), you’ll have to be a little more creative. Let’s just do that.

Count business days in R

There are some very creative ways to count business days, but the most convenient one is definitely by using the bizdays R package.

Calculating the number of business days can be done using the (identically named) bizdays function. It takes only three arguments that you’ll need to achieve your goals: (1) the start date, (2) the end data and (3) a calendar object.

A calendar object can created using the create.calendar function. In this object you pass arguments that define which days are business days and which aren’t:

• weekdays: A vector of characters that define which days of the week are not business days
• holidays: A vector of Dates that define which dates are not business days

By using the create.calendar function and the bizdays function, it’s fairly easy to count business days between two dates.

library(bizdays)
business_calendar <- create.calendar('my_calendar', weekdays = c('saturday','sunday'))

# data.table way
df[,n_days := bizdays(start_date, end_date, cal = business_calendar)]

# dplyr way
df %>% 
	mutate(n_days = bizdays(start_date, end_date, cal = business_calendar))

Add or subtract business days in R

In the next example, I do not want to count the number of days between two dates. I want to add or subtract some business days from a specific date. Using the bizdays library, that’s once again very easy. It contains an offset() function to add or subtract business days from a specific date. Here, too, you need to specify the calendar object you’d like to use.

A good tip is to specify the library with the function, because offset is a fairly used function name in other libraries.

library(bizdays)
business_calendar <- create.calendar('my_calendar', weekdays = c('saturday','sunday'))

# data.table way
df[,added_10_biz_days := bizdays::offset(my_date, 10, cal = business_calendar)] # add
df[,added_10_biz_days := bizdays::offset(my_date, -10, cal = business_calendar)] # subtract

# dplyr way
df %>% 
	mutate(added_10_biz_days = bizdays::offset(my_date, 10, cal = business_calendar)) # add
	mutate(added_10_biz_days = bizdays::offset(my_date, 10, cal = business_calendar)) # subtract

Great success!