How does one subtract hours from an NSDate?

Question

I would like to subtract 4 hours from a date. I read the date string into an NSDate object use the following code:

NSDateFormatter * dateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[dateFormatter setDateFormat:@"yyyy-MM-dd'T'HH:mm:ssZ"];
NSDate * mydate = [dateFormatter dateFromString:[dict objectForKey:@"published"]];

What do I do next?

(It's now 6 years, and 4 major versions of XCode later... and NSDate's functionality is still as unintuitive as in 2009 !!) — Mike Gledhill, Mar 17 '15 at 12:56

Georg Schölly · Answer 1 · 2012-01-06T14:46:31.760

49

NSDate *newDate = [theDate dateByAddingTimeInterval:-3600*4];

Link to documentation.

NSDate *newDate = [[[NSDate alloc] initWithTimeInterval:-3600*4
                                              sinceDate:theDate]] autorelease];

Link to documentation.

edited Jan 06 '12 at 14:46

answered Jul 21 '09 at 18:58

Georg Schölly

124,188
49
220
267

score 23 · Answer 2 · answered Jul 21 '09 at 18:47

23

NSCalendar is the general API for changing dates based on human time units. For this, you can use NSCalendar's -dateByAddingComponents:toDate:options: with a negative number of hours.

answered Jul 21 '09 at 18:47

Chuck

234,037
30
302
389

NSCalendar is not a recommended API to use. http://developer.apple.com/documentation/Cocoa/Reference/Foundation/Classes/NSCalendarDate_Class/Reference/Reference.html – oberbaum Feb 15 '10 at 15:59
10

@norskben: That page is for NSCalendar**Date**. That's what it says not to use. It specifically recommends NSCalendar as a replacement in the same note. – Chuck Feb 15 '10 at 17:17

score 9 · Answer 3 · answered May 15 '18 at 14:57

9

In Swift 4 :

var baseDate = ... // something
let dateMinus4Hours = Calendar.current.date(byAdding: .hour, value: -4, to: baseDate)

don't go with 24*3600 and stuff, that's asking for trouble.

answered May 15 '18 at 14:57

Guillaume Laurent

1,734
14
11

score 6 · Answer 4 · edited Aug 12 '16 at 17:34

6

Since iOS 8 there is the more convenient dateByAddingUnit:

Swift 2.x

//subtract 3 hours
let calendar = NSCalendar.autoupdatingCurrentCalendar()
newDate = calendar.dateByAddingUnit(.Hour, value: -3, toDate: originalDate, options: [])

edited Aug 12 '16 at 17:34

Bryan Bryce

1,310
1
16
29

answered May 10 '15 at 13:37

Ben Packard

26,102
25
102
183

1

Comment says subtract however 3 was used as value it should instead be -3 – naz Oct 16 '15 at 12:12

score 5 · Answer 5 · answered Dec 09 '16 at 07:32

5

//in Swift 3
//subtract 3 hours
let calendar = NSCalendar.autoupdatingCurrent
newDate = calendar.date(byAdding:.hour, value: -3, to: originalDate)

answered Dec 09 '16 at 07:32

Ning

148
1
10

score 2 · Answer 6 · answered May 04 '18 at 19:20

Here a function which might be useful as it returns the date -4 h considering that this may also change the date and the month and eventually the year. the .searchBackward option is the important part :)

public static func correctSecondComponent(date: Date, calendar: Calendar = Calendar(identifier: Calendar.Identifier.gregorian))->Date {

    let hour = calendar.component(.hour, from: date)

    let e = (calendar as NSCalendar).date(byAdding: NSCalendar.Unit.hour, value: -4, to: date, options:.searchBackwards)!

    return e
}

score 1 · Answer 7 · edited Mar 22 '18 at 20:05

1

dateFromString function returns NSDate, not NSString. you should change,

NSDate * theDate = [dateFormatter dateFromString:datetemp];

edited Mar 22 '18 at 20:05

Alexander Abakumov

13,617
16
88
129

answered Aug 05 '09 at 23:13

Guvener Gokce

804
14
20

How does one subtract hours from an NSDate?

7 Answers7

Linked

Related