How to Get Weekday And/Or Name of Month from a Nsdate Variable

How do I get weekday and/or name of month from a NSDate variable?

There is no need to manually convert to the Swedish words. iPhone will do it for you. Try this:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
dateFormatter.dateFormat = @"yyyyMMdd";
NSDate *date = [dateFormatter dateFromString:@"20111010"];

// set swedish locale
dateFormatter.locale=[[NSLocale alloc] initWithLocaleIdentifier:@"sv_SE"];

dateFormatter.dateFormat=@"MMMM";
NSString *monthString = [[dateFormatter stringFromDate:date] capitalizedString];
NSLog(@"month: %@", monthString);

dateFormatter.dateFormat=@"EEEE";
NSString *dayString = [[dateFormatter stringFromDate:date] capitalizedString];
NSLog(@"day: %@", dayString);

Output:

month: Oktober
day: Måndag

How to find weekday from today's date using NSDate?

NSCalendar* cal = [NSCalendar currentCalendar];
NSDateComponents* comp = [cal components:NSCalendarUnitWeekday fromDate:[NSDate date]];
return [comp weekday]; // 1 = Sunday, 2 = Monday, etc.

See @HuguesBR's answer if you just need the weekday without other components (requires iOS 8+).

NSInteger weekday = [[NSCalendar currentCalendar] component:NSCalendarUnitWeekday 
                                                   fromDate:[NSDate date]];

(If you don't get a correct answer, check if you have mistyped NSCalendarUnitWeekday with other week-related components like NSCalendarUnitWeekdayOrdinal, etc.)

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Swift 3:

let weekday = Calendar.current.component(.weekday, from: Date())
// 1 = Sunday, 2 = Monday, etc.

Get day of week using NSDate

What you are looking for (if I understand the question correctly) is NSCalendarUnit.CalendarUnitWeekday. The corresponding property of NSDateComponents is weekday.

Note also that your date format is wrong (the
full specification can be found here: http://unicode.org/reports/tr35/tr35-6.html).

The function can be simplified slightly, using automatic type inference, also you use variables a lot where constants are sufficient.
In addition, the function should return an optional which is nil
for an invalid input string.

Updated code for Swift 3 and later:

func getDayOfWeek(_ today:String) -> Int? {
    let formatter  = DateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    guard let todayDate = formatter.date(from: today) else { return nil }
    let myCalendar = Calendar(identifier: .gregorian)
    let weekDay = myCalendar.component(.weekday, from: todayDate)
    return weekDay
}

Example:

if let weekday = getDayOfWeek("2014-08-27") {
    print(weekday)
} else {
    print("bad input")
}

Original answer for Swift 2:

func getDayOfWeek(today:String)->Int? {

    let formatter  = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    if let todayDate = formatter.dateFromString(today) {
        let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
        let myComponents = myCalendar.components(.Weekday, fromDate: todayDate)
        let weekDay = myComponents.weekday
        return weekDay
    } else {
        return nil
    }
}

Objective C - How can i get the weekday from NSDate?

Edit for Mac:

The format of the string has to be —YYYY-MM-DD HH:MM:SS ±HHMM according to the docs, all fields mandatory

Old answer (for iPhone and tested on simulator):

There is no (public) -initWithString: method in NSDate, and what you get returned is not what you expect.

Use a properly configured (you need to give the input format) NSDateFormatter and -dateFromString:.

How to get the day name from a selected date in swift?]

To get the weekday do the following:

let dateFormatter = DateFormatter()
var weekday: String = ""
dateFormatter.dateFormat = "cccc"
weekday = dateFormatter.string(from: date)

Read more about the different formats here:
http://userguide.icu-project.org/formatparse/datetime

Find weekday of a date given the month start weekday

It is hard to use modular arithmetic if you don't start counting from zero.

So let's define some new variables:

W = X - 1 = the weekday number, where W = 0 means Sunday

D = Y - 1 = the day of the month, starting with 0

Then W + D is the weekday number (Sunday = 0) of day D, if W + D < 7.

So take (W + D) mod 7 to get the weekday number of day D. Add 1 to convert back to Sunday = 1, so ((W + D) mod 7) + 1.

Substitute the definitions of W and D.

Weekday number of day X (where Sunday = 1) = ((X - 1 + Y - 1) mod 7) + 1 = ((X + Y - 2) mod 7) + 1.

How do I get the name of a day of the week in the user's locale?

An NSDateFormatter can give you the list of names:

NSDateFormatter * df = [[NSDateFormatter alloc] init];
[df setLocale: [NSLocale currentLocale]];
NSArray * weekdays = [df weekdaySymbols];

Which you can then index like any other array [weekdays objectAtIndex:dayIdx]; Be aware, however, that the first weekday may differ by locale; exactly how it may vary (along with many other things about NSCalendar) is not particularly well-explained in the docs.

How to extract today, yesterday from Date() and make it localised like weekday and months?

DateFormatter has special flag for that: doesRelativeDateFormatting, which renders dates in relative format, using locale set for this formatter.

… If a date formatter uses relative date formatting, where possible it
replaces the date component of its output with a phrase—such as
“today” or “tomorrow”—that indicates a relative date. The available
phrases depend on the locale for the date formatter; whereas, for
dates in the future, English may only allow “tomorrow,” French may
allow “the day after the day after tomorrow,” …

Example:

let dateFormatter = DateFormatter()
dateFormatter.locale = Locale.autoupdatingCurrent // Using system locale
dateFormatter.doesRelativeDateFormatting = true // Enabling relative date formatting

// other dataFormatter settings here, irrelevant for example
dateFormatter.timeStyle = .none
dateFormatter.dateStyle = .medium

let now = Date() 
let dateString: String = dateFormatter.string(from: now)  
print("dateString: \(dateString)") // Prints `dateString: <Today in current locale>`

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