Adding/Reducing day in the Date object returns wrong date when day light savings time ends

Question

I'm using

Calendar.current.date(byAdding: .day, value: -1, to: somedate) ?? somedate

to reduce 1 day from some date. Since Daylight Saving Time Ended on 1'st Nov, 2020. When i'm trying to do this on 2nd Nov, 2020 0hr:0m:0s's date object, i expect it to return 1st Nov, 2020 0hr:0m:0s, but instead it is returning 31st Oct, 2020 23hr:0m:0s.

Is it something i'm doing wrong or is it some other issue?

How to reproduce:-

Create a date object using time stamp 1604275200. using Date(timeIntervalSince1970: 1604275200)
Change timezone of ur device to some place where daylight savings time is considered. i tried it in HST timezone
Try reducing the day using the above given method.
You'll see date returning as 31st Oct.


extension Date {
    init(timeIntervalInMillis: Double) {
        self.init(timeIntervalSince1970: timeIntervalInMillis / 1000)
    }
    func add(_ component: Calendar.Component, value: Int) -> Date {
        return Calendar.current.date(byAdding: .day, value: value, to: self) ?? self
    }
    var noon: Date {
        return Calendar.current.date(bySettingHour: 12, minute: 0, second: 0, of: self)!
    }
}
print(Calendar.current.timeZone.identifier)
let date = Date(timeIntervalInMillis: 1604275200000)
print("Date is ",date)
print("Yesterday's date is ",date.add(.day, value: -1))
print("Noon time is ",date.noon)
print("Yesterday date from noon's date is ",date.noon.add(.day, value: -1))

Output:

America/Chicago
Date is  2020-11-02 00:00:00 +0000
Yesterday's date is  2020-10-31 23:00:00 +0000
Noon time is  2020-11-01 18:00:00 +0000
Yesterday date from noon's date is  2020-10-31 17:00:00 +0000

Any help would be appreciated.

Leo Dabus · Answer 1 · 2020-11-03T08:24:36.813

0

edit/update:

There is nothing wrong with your code. Your issue is that you are printing the UTC date representation instead of using DateFormatter with the time zone set to chicago to show the resulting date at the desired timezone.

print("Date is ",date)  // Date is  2020-11-02 00:00:00 +0000\n"
print("Yesterday's date is ",date.add(.day, value: -1))  // "Yesterday's date is  2020-10-31 23:00:00 +0000\n"  
print("Noon time is ",date.noon) // "Noon time is  2020-11-01 18:00:00 +0000\n"
print("Yesterday date from noon's date is ",date.noon.add(.day, value: -1)) // "Yesterday date from noon's date is  2020-10-31 17:00:00 +0000\n"

let fmter = DateFormatter()
fmter.timeZone = TimeZone(identifier: "America/Chicago")!
fmter.dateStyle = .full
fmter.timeStyle = .full

print("Date is ", fmter.string(from: date))  // "Date is  Sunday, 1 November 2020 18:00:00 Central Standard Time\n"
print("Yesterday's date is ", fmter.string(from: date.add(.day, value: -1)))  // "Yesterday's date is  Saturday, 31 October 2020 18:00:00 Central Daylight Time\n"
print("Noon time is ", fmter.string(from: date.noon))  // "Noon time is  Sunday, 1 November 2020 12:00:00 Central Standard Time\n"
print("Yesterday date from noon's date is ",fmter.string(from: date.noon.add(.day, value: -1)))  // "Yesterday date from noon's date is  Saturday, 31 October 2020 12:00:00 Central Daylight Time\n"

edited Nov 03 '20 at 08:24

answered Nov 03 '20 at 06:26

Leo Dabus

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My requirement is that i need to use midnights time (the start of day). In any case the returned date object for 2nd Nov should be 31st Oct. In other cases its giving correct response. – aman Nov 03 '20 at 07:12
Just use noon and get the start of day for the resulting date https://stackoverflow.com/a/44009988/2303865 – Leo Dabus Nov 03 '20 at 07:15
What is your timezone identifier? Please add a [mcve] There is no way to subtract 1 day from noon and result in a different time/date – Leo Dabus Nov 03 '20 at 07:30
I used this timezone identifier "HST". i have updated the question with further details. – aman Nov 03 '20 at 07:38
Updated it. the identifier is America/Chicago – aman Nov 03 '20 at 07:52
not related to your question but timezone in your add method is pointless and you should use the value not -1 `func add(_ component: Calendar.Component, value: Int) -> Date {` `Calendar.current.date(byAdding: .day, value: value, to: self)!` `}` – Leo Dabus Nov 03 '20 at 08:04
Not working for my case. I tried ur solution for this, same issue. Can u pls try it once ur side. – aman Nov 03 '20 at 08:04
@aman there is nothing wrong with your code. Your issue is that you are not using DateFormatter with the time zone set to chicago to show the resulting date – Leo Dabus Nov 03 '20 at 08:19
Still same thing bro.:( – aman Nov 03 '20 at 08:24
As I said there is nothing wrong with your code. Check my last edit – Leo Dabus Nov 03 '20 at 08:28

Adding/Reducing day in the Date object returns wrong date when day light savings time ends

1 Answers1