How to disable past date in ckcalendar?

I am looking for how to disable past dates in the CKCalendar. For instance, I want to disable all dates before the current date. Only today's date and the future date must be clickable.

In addition to Larme's comment (setting calendar:willSelectDate to return NO for past dates), if you want to configure the colors for those "disabled dates", you can do so by setting up the delegate method configureDateItem: forDate:.

An example:

- (void)calendar:(CKCalendarView *)calendar configureDateItem:(CKDateItem *)dateItem forDate:(NSDate *)date {

    if([date laterDate:minimumDate] == minimumDate) {
        dateItem.textColor = [UIColor grayColor];
    }
}

The above code sets the text color of all past dates to gray.

An example for willSelectDate delegate method:

- (BOOL)calendar:(CKCalendarView *)calendar willSelectDate:(NSDate *)date {
    if ([date laterDate:minimumDate] == minimumDate) {
        return NO;
    }
    return [calendar dateIsInCurrentMonth:date];
}

The above code disables selection of all past dates.