The calendar file is a xml file like the one JDemetra+ would write when defining a calendar in the Graphical User Interface.
Examples
file <- system.file("workspaces", "workspace_test", "Calendars", "Calendars.xml", package = "rjd3workspace")
my_calendar <- read_calendars(file)
my_calendar
#> $Test_Calendar
#> Holiday:
#> - Fixed day: month=1, day=1
#> - Fixed day: month=5, day=1
#> - Prespecified holiday: event=EASTERMONDAY
#> - Prespecified holiday: event=ASCENSION
#> - Prespecified holiday: event=WHITMONDAY
#>
#> Mean correction: Yes
#>