NSCalendar is a mighty class which let you do a lot of different things with NSDate. At first it might look a bit complicated but with some time it gets very useful when working with dates (especially with NSDateFormatter). As language I will use Objective-C but translating it to Swift shouldn’t be too hard.

So if you want to know which day of a week a particular NSDate is you have to create a NSCalendar to work with. To do all the date related stuff you also need a NSDateComponents object where you define how to work with the calendar. With them we create dates for a particular week in were our date is and loop through them. In every iteration we check if the created date is the same as our original date. I’ve created a function for date comparisons since I need them regularly often in my app. You basically just compare the single components like day, month, year, hour, minute,…

//Create our NSCalendar to work with
NSCalendar *gregorian = [[NSCalendar alloc]
                             initWithCalendarIdentifier:NSCalendarIdentifierGregorian];

    //Week starts on Monday in Europe! People in the US can comment the following line out.
    [gregorian setFirstWeekday:2];
    
    //get today
    NSDate* today = [NSDate date];
    
    //We need the dateComponents to do work with our NSCalendar
    NSDateComponents *dateComponents = [gregorian components:(NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitWeekOfYear | NSCalendarUnitWeekday ) fromDate:today];
    
    // Loop through week
    for (int i = 2; i < 9; i++) {
        //Set the weekday and create a new date from it
        [dateComponents setWeekday:i];
        NSDate *weekDay = [gregorian dateFromComponents:dateComponents];
    
        //Compare the new date with our "today"
        if ([DateFunctions isDate:weekDay equalWith:today]) 
        {
           //Do your stuff here, day of the week is i
        }
    }

So with this little piece of code you are able to determine which day of the week your NSDate object is. I hope this will be helpful for you, if you have any questions feel free to use the comments below!