NSDate returns an invalid week.

Question

I have the following code:

getWeek(addDays(Date, amount: 6))

func addDays(date: NSDate, amount: Int) -> NSDate {
    // calculation $additionalDays
    let additionalDays = amount
    // adding $additionalDays
    let components = NSDateComponents()
    components.day = additionalDays

    // important: NSCalendarOptions(0)
     let futureDate = NSCalendar.currentCalendar()
    .dateByAddingComponents(components, toDate: date, options: NSCalendarOptions(rawValue: 0))
    return futureDate!
}

func getWeek(today:NSDate)->Int? {
    let formatter = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierGregorian)!
    let myComponents = myCalendar.components(.WeekOfYear, fromDate: today)
    let weekNumber = myComponents.weekOfYear
   return weekNumber
}

Date in getWeek(addDays(Date, amount: 6))returns dec 27, 2015, 7:16PM This is correct (next Sunday) However, if I try to return the week number for this date, it returns 1, then it should be 53. How can I get the correct week number?

Answer 1

According to Apple Developer Technical Support :

December 27, 2015 is week 52, not week 53. The first day of week 53 in 2015 is December 28.

, , , getWeek(), ISO 8601. , NSCalendarIdentifierGregorian, NSCalendarIdentifierISO8601. /lots/ . gory, , " - , , 8601, NSCalendarIdentifierISO8601.

getWeek() , ISO 8601. :

print(self.getWeek(self.dateFromFixedFormatString("2015-12-27 12:34")))
print(self.getWeek(self.dateFromFixedFormatString("2015-12-28 12:34")))

• 52
• 53

:

func dateFromFixedFormatString(dateStr: String) -> NSDate {
   let df = NSDateFormatter()
   df.locale = NSLocale(localeIdentifier: "en_US_POSIX")
   df.dateFormat = "yyyy-MM-dd HH:mm"
   return df.dateFromString(dateStr)!
}
func getWeek(today:NSDate) -> Int {
   let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierISO8601)!
   let myComponents = myCalendar.components(.WeekOfYear, fromDate: today)
   let weekNumber = myComponents.weekOfYear
   return weekNumber
}

, , GregorianCalendar, , NSCalendarIdentifierISO8601 . NSCalendar.currentCalendar() ISO. ( )

Answer 2

​​ Apple. , Apple , 27 2015 1 2016 . ISO 53, 31 . (A 31 1: https://en.wikipedia.org/wiki/ISO_week_date#Last_week).

, , , . , .YearForWeekOfYear, 2016 1 .

Answer 3

Please keep in mind that the ISO week and US numbering are different! If you look at the Wikipedia article mentioned above, read on to “Other Numbering Systems per Week”. Therefore, there must be a setting to control US and ISO weeks.

Answer 4

I made your program with minor corrections and changed the calendar to ISO. This provides the desired result for 2015, please check it in other years.

import Foundation

let now = NSDate()

func addDays(date: NSDate, amount: Int) -> NSDate {
    // calculation $additionalDays
    let additionalDays = amount
    // adding $additionalDays
    let components = NSDateComponents()
    components.day = additionalDays

    // important: NSCalendarOptions(0)
    let futureDate = NSCalendar.currentCalendar()
        .dateByAddingComponents(components, toDate: date, options: NSCalendarOptions(rawValue: 0))
    return futureDate!
}

func getWeek(today:NSDate)->Int {
    let formatter = NSDateFormatter()
    formatter.dateFormat = "yyyy-MM-dd"
    let myCalendar = NSCalendar(calendarIdentifier: NSCalendarIdentifierISO8601)!
    let myComponents = myCalendar.components(.WeekOfYear, fromDate: today)
    let weekNumber = myComponents.weekOfYear
    return weekNumber
}

print(getWeek(addDays(now, amount: 6)))