Date selected from UIDatePicker is different from the date being saved

Question

This is how I setup my datePicker

self.datePicker = [[UIDatePicker alloc] init];
self.datePicker.timeZone = [NSTimeZone localTimeZone];

This is how I save the date that I selected

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateStyle:NSDateFormatterMediumStyle];
[formatter setTimeZone:[NSTimeZone localTimeZone]];
dateToSave = [formatter dateFromString:self.dateTextField.text];
NSLog(@"date saved = %@", dateToSave);

If I select Nov 18 2013 from the date picker, the NSLog shows

date saved = 2013-11-17 16:00:00 +0000

However, somewhere in my code, I need to get the difference in days between today's date and the date that I selected in the datepicker.

NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSDayCalendarUnit fromDate:[NSDate date] toDate:dateSaved options:0];
NSLog(@"number of days => %i", [dateComponents day]);

Today is Nov 10. The date I saved is Nov 18. But the number of days difference is 7, instead of 8.

possible duplicate of [Why NSDate is reporting the wrong date?](http://stackoverflow.com/questions/6741519/why-nsdate-is-reporting-the-wrong-date) — Martin R, Nov 10 '13 at 10:12
Or http://stackoverflow.com/questions/14550249/uidatepicker-giving-wrong-time, http://stackoverflow.com/questions/8466744/getting-date-from-nsdate-date-off-by-a-few-hours, and some more. — Martin R, Nov 10 '13 at 10:15
What are the values of `[NSDate date]` and `dateSaved` when calculating the difference? — Martin R, Nov 10 '13 at 10:28
the date that I saved is ... 2013-11-17 16:00:00 +0000 today's date is ... 2013-11-10 10:36:55 +0000 — iPhoneJavaDev, Nov 10 '13 at 10:37
As I mentioned in my answer, please try to use [NSTimeZone timeZoneForSecondsFromGMT:0]. — Sviatoslav Yakymiv, Nov 10 '13 at 10:59
@SviatoslavYakymiv: I do not think that makes sense. Calculating the number of days should be done in the local time zone, not in GMT. The result can be different due to daylight saving time. — Martin R, Nov 10 '13 at 11:04

Sviatoslav Yakymiv · Answer 1 · 2013-11-10T10:22:19.693

2

Your time zone is -8. 2013-11-17 16:00:00 +0000 equals to 2013-11-18 00:00:00 -0800.

Use [NSTimeZone timeZoneForSecondsFromGMT:0] instead of [NSTimeZone localTimeZone]

edited Nov 10 '13 at 10:22

answered Nov 10 '13 at 10:06

Sviatoslav Yakymiv

7,887
2
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I updated my question. Sorry but the actual problem is when I tried to get the difference between today's date and the date that I saved. – iPhoneJavaDev Nov 10 '13 at 10:19
i tried it but the [dateComponents day] still returns me 7 instead of 8 – iPhoneJavaDev Nov 10 '13 at 10:31
Try to log both dates. i think you'll see the difference. – Sviatoslav Yakymiv Nov 10 '13 at 10:35

Martin R · Accepted Answer · 2013-11-10T10:56:15.053

(This answer refers to the updated question about calculating the number of days between two dates.)

The problem is that [NSDate date] is the current date+time, not the start of the current day. For example, if

 [NSDate date] = "2013-11-10 10:00:00"
 dateSaved     = "2013-11-18 00:00:00"    (both in your *local* timezone)

then the difference between these two dates is "7 days and 14 hours". Therefore you get 7 as the number of days.

So you have to calculate the start of the current day first:

NSDate *startOfDay;
[[NSCalendar currentCalendar] rangeOfUnit:NSDayCalendarUnit
                                startDate:&startOfDay
                                 interval:NULL
                                  forDate:[NSDate date]];

and then use it in the calculation of the difference:

NSDateComponents *dateComponents = [[NSCalendar currentCalendar] components:NSDayCalendarUnit
                                           fromDate:startOfDay
                                             toDate:dateSaved
                                            options:0];

given exactly the same code that i used for my datepicker and the way i saved the selected date, and given today is Nov 10 7:28pm, and the date i saved is Nov 18, this is what i got... date saved = 2013-11-17 16:00:00 +0000 date today = 2013-11-09 16:00:00 +0000 i got the correct difference in days, so i guess the above is correct right? — iPhoneJavaDev, Nov 10 '13 at 11:30
@iPhoneJavaDev: Is "date today = 2013-11-09 16:00:00 +0000" what you calculated with the code from my answer? Yes, that looks correct, because that is "2013-11-10 00:00:00" in your local timezone. — Martin R, Nov 10 '13 at 11:34

score 0 · Answer 3 · edited May 23 '14 at 06:38

0

NSDateFormatter *date_form=[[NSDateFormatter alloc]init];

[date_form setDateFormat:@"dd/MM/yyyy"];

NSDate *seletected_date = [datepicker date];

NSString *dateToSave=[[NSString alloc] initWithFormat:@"%@",[date_form stringFromDate:seletected_date]]; 

NSLog(@"date saved = %@", dateToSave);

Remove localtimezone

edited May 23 '14 at 06:38

Hiren

12,720
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answered Nov 10 '13 at 10:11

Parthi

99
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Date selected from UIDatePicker is different from the date being saved

3 Answers3