public static DayOfWeekFunction newDayOfWeek(GroupingExpression exp) {
        return new DayOfWeekFunction(exp);
    }
Creates a new instance of {@link DayOfWeekFunction} for the given {@link GroupingExpression}.

@param exp The expression to evaluate, must evaluate to a long.
@return The created function node.
container-search/src/main/java/com/yahoo/search/grouping/request/TimeFunctions.java