NSCalendar first day of week

Question

Does anyone know if there is a way to set the first day of the week on a NSCalendar, or is there a calendar that already has Monday as the first day of the week, instead of Sunday. I'm currently working on an app that is based around a week's worth of work, and it needs to start on Monday, not Sunday. I can most likely do some work to work around this, but there will be a lot of corner cases. I'd prefer the platform do it for me.

Thanks in advance

Here's some the code that I'm using. it's saturday now, so what I would hope is that weekday would be 6, instead of 7. that would mean that Sunday would be 7 instead of rolling over to 0

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian setFirstWeekday:0];
unsigned unitFlags = NSYearCalendarUnit | NSMonthCalendarUnit |  NSDayCalendarUnit | NSWeekCalendarUnit | NSWeekdayCalendarUnit;
NSDateComponents *todaysDate = [gregorian components:unitFlags fromDate:[NSDate date]];
int dayOfWeek = todaysDate.weekday;

Answer 1

… is there a calendar that already has Monday as the first day of the week, instead of Sunday.

Someday, there will be.

Answer 2

I've done it like this.

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
NSDate *today = [NSDate date];
NSDateComponents *compForWeekday = [gregorian components:(NSWeekdayCalendarUnit) fromDate:today];
NSInteger weekDayAsNumber = [compForWeekday weekday]; // The week day as number but with sunday starting as 1

weekDayAsNumber = ((weekDayAsNumber + 5) % 7) + 1; // Transforming so that monday = 1 and sunday = 7

Answer 3

Edit: This does not check the edge case where the beginning of the week starts in the prior month. Some updated code to cover this: https://stackoverflow.com/a/14688780/308315

---

In case anyone is still paying attention to this, you need to use

ordinalityOfUnit:inUnit:forDate:

and set firstWeekday to 2. (1 == Sunday and 7 == Saturday)

Here's the code:

NSCalendar *gregorian = [[[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar] autorelease];
[gregorian setFirstWeekday:2]; // Sunday == 1, Saturday == 7
NSUInteger adjustedWeekdayOrdinal = [gregorian ordinalityOfUnit:NSWeekdayCalendarUnit inUnit:NSWeekCalendarUnit forDate:[NSDate date]];
NSLog(@"Adjusted weekday ordinal: %d", adjustedWeekdayOrdinal);

Remember, the ordinals for weekdays start at 1 for the first day of the week, not zero.

Documentation link.

Answer 4

In my opinion this settings should be dynamic according to the user locale. Therefore one should use:

NSCalendar *gregorian = [[NSCalendar alloc] initWithCalendarIdentifier:NSGregorianCalendar];
[gregorian setLocale:[NSLocale currentLocale]];

This will cause the calendar to set the first week day according to the user locale automatically. Unless you are developing your app for a specific purpose/user locale (or prefer to allow the user to choose this day).

Answer 5

I had trouble with a lot of the answers here. . maybe it was just me. .

Here's an answer that works for me:

- (NSDate*)firstDayOfWeek
{
    NSCalendar* cal = [[NSCalendar currentCalendar] copy];
    [cal setFirstWeekday:2]; //Override locale to make week start on Monday
    NSDate* startOfTheWeek;
    NSTimeInterval interval;
    [cal rangeOfUnit:NSWeekCalendarUnit startDate:&startOfTheWeek interval:&interval forDate:self];
    return startOfTheWeek;
}

- (NSDate*)lastDayOfWeek
{
    NSCalendar* cal = [[NSCalendar currentCalendar] copy];
    [cal setFirstWeekday:2]; //Override locale to make week start on Monday
    NSDate* startOfTheWeek;
    NSTimeInterval interval;
    [cal rangeOfUnit:NSWeekCalendarUnit startDate:&startOfTheWeek interval:&interval forDate:self];
    return [startOfTheWeek dateByAddingTimeInterval:interval - 1];
}

Update:

As pointed out (elsewhere) by @vikingosegundo, in general its best to let the local determine which day is the start of the week, however in this case the OP was asking for the start of the week to occur on Monday, hence we copy the system calendar, and override the firstWeekDay.