Cldr.Calendar.week_of_month
You're seeing just the callback
week_of_month, go back to Cldr.Calendar module for more information.
Specs
week_of_month(Calendar.year(), week(), Calendar.day()) :: {Calendar.month(), week()} | {:error, :not_defined}
Returns a tuple of {month, week_in_month} for a given year, month or week, and day
for a a calendar.
The week_in_month is calculated based upon the calendar configuration.