NSDate day of the year (swift)

Question

How might the day number of the year be found with swift? Is there a simple way that I'm not seeing, or do I have to find the number of seconds from Jan 1 to the current date and divide by the number of seconds in a day?

score 60 · Accepted Answer · edited May 23 '17 at 12:17

60

This is a translation of the answer to How do you calculate the day of the year for a specific date in Objective-C? to Swift.

Swift 2:

let date = NSDate() // now
let cal = NSCalendar.currentCalendar()
let day = cal.ordinalityOfUnit(.Day, inUnit: .Year, forDate: date)
print(day)

Swift 3:

let date = Date() // now
let cal = Calendar.current
let day = cal.ordinality(of: .day, in: .year, for: date)
print(day)

This gives 1 for the first day in the year, and 56 = 31 + 25 for today (Feb 25).

... or do I have to find the number of seconds from Jan 1 to the current date and divide by the number of seconds in a day

This would be a wrong approach, because a day does not have a fixed number of seconds (transition from or to Daylight Saving Time).

edited May 23 '17 at 12:17

Community

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answered Feb 25 '15 at 07:08

Martin R

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why does your method returns 56 mine 55 ? – Leo Dabus Feb 25 '15 at 07:13
@LeonardoSavioDabus: See updated answer: This method returns 1 for the first day in the year. – Martin R Feb 25 '15 at 07:13
NSCalendar.currentCalendar().ordinalityOfUnit(.CalendarUnitDay, inUnit: .CalendarUnitYear, forDate: NSDate() ) – Leo Dabus Feb 25 '15 at 07:14
perfect thank you, ordinalityOfUnit, no wonder I couldn't find it – Dan Oswalt Feb 25 '15 at 07:15
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@LeonardoSavioDabus: Yes of course (and you could write an extension for it, SCNR :) – I prefer multiple shorter statements in the answer, as they are better readable. – Martin R Feb 25 '15 at 07:15
when I run this I get 55, shouldn't i get 56? – Dan Oswalt Feb 25 '15 at 07:20
@zbnrg: I get 56 (and Leonardo as well, as it seems). – Martin R Feb 25 '15 at 07:21
@Martin R That's correct 55 using mine and 56 using yours – Leo Dabus Feb 25 '15 at 07:22
hm, okay, well it works for my purposes anyhow, thank you both – Dan Oswalt Feb 25 '15 at 07:23
Not working in Swift 2, compiler throws error: "Type of expression is ambiguous without more context" – ixany Sep 11 '15 at 19:16
@mrtn.lxo: Yes, the definition of calendar units changed with Swift 2. I have extended the answer for Swift 2, thanks for the feedback! – Martin R Sep 11 '15 at 19:20

score 15 · Answer 2 · answered Mar 06 '17 at 10:24

15

Swift 3

extension Date {
    var dayOfYear: Int {
        return Calendar.current.ordinality(of: .day, in: .year, for: self)!
    }
}

use like

Date().dayOfYear

answered Mar 06 '17 at 10:24

Adam Smaka

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score 4 · Answer 3 · answered Feb 25 '15 at 07:06

Not at all !!! All you have to do is to use NSCalendar to help you do your calendar calculations as follow:

let firstDayOfTheYear  = NSCalendar.currentCalendar().dateWithEra(1, year: NSCalendar.currentCalendar().component(.CalendarUnitYear, fromDate: NSDate()), month: 1, day: 1, hour: 0, minute: 0, second: 0, nanosecond: 0)!   // "Jan 1, 2015, 12:00 AM"

let daysFromJanFirst = NSCalendar.currentCalendar().components(.CalendarUnitDay, fromDate: firstDayOfTheYear, toDate: NSDate(), options: nil).day   // 55

let secondsFromJanFirst = NSCalendar.currentCalendar().components(.CalendarUnitSecond, fromDate: firstDayOfTheYear, toDate: NSDate(), options: nil).second   // 4,770,357

score 0 · Answer 4 · answered Feb 25 '15 at 07:15

0

You can find the number of days since your date like this:

let date = NSDate() // your date

let days = cal.ordinalityOfUnit(.CalendarUnitDay, inUnit: .CalendarUnitYear, forDate: date)

println(days)

answered Feb 25 '15 at 07:15

Kanan Vora

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It is object of NSCalendar – Kanan Vora Feb 25 '15 at 08:33

NSDate day of the year (swift)

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