NSDateFormatter subtracting a day when removing time

Question

I am trying to remove time from date using NSDateFormatter. This is the code:

func dateWithOutTime( datDate: NSDate?) -> NSDate {

    let formatter = NSDateFormatter()
    formatter.dateFormat = "dd-MM-yyyy"
    let stringDate: String = formatter.stringFromDate(datDate!)
    let dateFromString = formatter.dateFromString(stringDate)

return dateFromString!
}

If i send in ex 04-01-2016 12:00:00, the return is 03-01-2016 23:00:00 I have tried changing the dateFormat, but it still keeps to subtracting a day from the date... Why? Please Help :)

Use date formatter to display your local time or descriptionWithLocale to know the time at your timezone — Leo Dabus, Jan 04 '16 at 12:50
Btw you should use noon instead of midnight for "don't care time" date calculations — Leo Dabus, Jan 04 '16 at 12:54
if you really need the first time of the day you need to use NSCalendar method startOfDayForDate — Leo Dabus, Jan 04 '16 at 13:07
Why do you declare the function parameter as optional since you're going to unwrap the optional forced anyway? — vadian, Jan 04 '16 at 13:33
The result is absolutely correct but you are checking it the wrong way. — Sulthan, Jan 04 '16 at 13:45
I didn't quite understand descriptionWithLocale.. Im fetching records from CoreData and want to get records between two dates ignoring the time, so the date must be in NSDate-format, not string. — Vegar Flo, Jan 04 '16 at 13:56
Again don't use midnight use noon using the method dateBySettingHour to 12pm http://stackoverflow.com/a/30816316/2303865 — Leo Dabus, Jan 04 '16 at 14:24

vadian · Accepted Answer · 2017-11-13T12:36:04.453

7

The easiest way is to use startOfDayForDate of NSCalendar

Swift 2:

func dateWithOutTime( datDate: NSDate) -> NSDate {
    return NSCalendar.currentCalendar().startOfDayForDate(datDate)
}

Swift 3+:

func dateWithOutTime(datDate: Date) -> Date {
    return Calendar.current.startOfDay(for: datDate)
}

or to adjust the time zone to UTC/GMT

Swift 2:

func dateWithOutTime( datDate: NSDate) -> NSDate {
  let calendar = NSCalendar(identifier: NSCalendarIdentifierGregorian)!
  calendar.timeZone = NSTimeZone(forSecondsFromGMT: 0)
  return calendar.startOfDayForDate(datDate)
}

Swift 3+:

func dateWithOutTime(datDate: Date) -> Date {
  var calendar = Calendar(identifier: .gregorian)
  calendar.timeZone = TimeZone(secondsFromGMT: 0)!
  return calendar.startOfDay(for: datDate)
}

edited Nov 13 '17 at 12:36

answered Jan 04 '16 at 13:26

vadian

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Thank you. This was much smoother than using the formatter... But it still returns one day less than the date, and time set to 23:00:00 – Vegar Flo Jan 04 '16 at 13:58
2

Your time zone is probably UTC +1 so actually the time is correct. If you really need UTC time set the time zone of the calendar. I updated the answer. – vadian Jan 04 '16 at 14:07
Thanks again! You are correct about me being +1 from UTC. With your updated answer everything shows up correct. – Vegar Flo Jan 04 '16 at 14:28
@VegarFlo don't use startOfDayForDate it might not return 12am – Leo Dabus Jan 04 '16 at 14:29
@VegarFlo no need to use GMT time – Leo Dabus Jan 04 '16 at 14:31
But you also said in your comment to use this? – Vegar Flo Jan 04 '16 at 14:39

score 1 · Answer 2 · answered Jan 04 '16 at 13:11

Two things:

(a) This can be done without using NSDateFormatter. (b) Calling print(aDate) will give you the UTC time, not in your local time. After losing too many brain cells trying to mentally convert back and forth, I decided to make an extension to NSDate to print it in my local timezone.

// NSDateFormatter is expensive to create. Create it once and reuse
let dateFormatter = NSDateFormatter()
dateFormatter.locale = NSLocale.currentLocale()
dateFormatter.dateFormat = "yyyy-MM-dd HH:mm:ss ZZZZ"

extension NSDate {
    // This will print the date in the local timezone
    var localTime: String {
        return dateFormatter.stringFromDate(self)
    }
}

func dateWithOutTime(datDate: NSDate?) -> NSDate {
    let calendar = NSCalendar.currentCalendar()
    let components = calendar.components([.Year, .Month, .Day], fromDate: datDate!)
    return calendar.dateFromComponents(components)!
}

let datDate = NSCalendar.currentCalendar().dateWithEra(1, year: 2016, month: 1, day: 4, hour: 12, minute: 0, second: 0, nanosecond: 0)
let result = dateWithOutTime(datDate)
print(result.localTime)

Thank you! What you say about calling print explains my trouble. Live in Norway and are 1 hour in front of UTC. Does this mean that on my phone the date would be "correct" and computer shows "wrong"? — Vegar Flo, Jan 04 '16 at 14:07
`23:00 UTC = 00:00 CET`, they both represent the same moment in time. `print` always show the UTC so unless you live in the British Isles, it will give you "wrong" output every time. — Code Different, Jan 04 '16 at 14:15
You are using date formatter and stating that it can be done without it — Leo Dabus, Jan 04 '16 at 14:20
Btw date formatter default it is local time so you don't need to specify it again — Leo Dabus, Jan 04 '16 at 14:33

NSDateFormatter subtracting a day when removing time

2 Answers2