SWI-Prolog -- day_of_the

Documentation
- Reference manual
  - Built-in Predicates
    - Operating System Interaction
      - Dealing with time and date
        
        Time and date predicates
        
        get_time/1
        
        stamp_date_time/3
        
        date_time_stamp/2
        
        date_time_value/3
        
        format_time/3
        
        format_time/4
        
        parse_time/2
        
        parse_time/3
        
        day_of_the_week/2
- Packages

Availability::- use_module(library(date)).(can be autoloaded)

day_of_the_week(+Date,-DayOfTheWeek)

Computes the day of the week for a given date. Date = date(Year,Month,Day). Days of the week are numbered from one to seven: Monday = 1, Tuesday = 2, ... , Sunday = 7.