Format RFC3339 dates

Question

I am receiving the following date in string format from the API

2015-04-18 06:08:28.000000

I want the date to be in the format of d/M/yyyy

I tried the following

NSString *datevalue = (NSString*)value;
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"d/M/yyyy"];
NSDate *date =  [formatter dateFromString:datevalue];
NSString *currentDate = [formatter stringFromDate:date];

This returns NIL, what could be the possible issue, or how do i format such dates in objective-c?

Thanks.

Do you have any control over the API's format for dates? Often RFC 3339/ISO 8601 dates include a `Z` at the end (to make it explicit that it is GMT/UTC/Zulu). And often there is a `T` between the date and year. You can use whatever format you want, but a common convention would be `2015-04-18T06:08:28.000000Z`. — Rob, Apr 19 '15 at 18:03
The format string you use to read the character date should look vaguely like the string you're reading!! http://www.unicode.org/reports/tr35/tr35-31/tr35-dates.html#Date_Format_Patterns — Hot Licks, Apr 19 '15 at 23:59
Thanks @Rob, I have control over the API server, I'll have a look — Ibrahim Azhar Armar, Apr 20 '15 at 03:25

Black Frog · Answer 1 · 2015-04-19T16:48:09.557

You cannot use the same formatter for read and writing the date string because they are the different. The format for your input date is incorrect.

// input string date: 2015-04-18 06:08:28.000000
// [formatter setDateFormat:@"d/M/yyyy"]; // incorrect
[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSSSSS"];

Below is sample code

//
//  main.m
//  so29732496
//
//  Created on 4/19/15.
//

#import <Foundation/Foundation.h>

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        NSLog(@"Hello, World!");

        NSString *dateStringFromAPI = @"2015-04-18 06:08:28.000000";
        NSString * const kAPIDateFormat = @"yyyy-MM-dd HH:mm:ss.SSSSSS";

        // convert API date string
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        [formatter setDateFormat:kAPIDateFormat];
        NSDate *apiDate =  [formatter dateFromString:dateStringFromAPI];


        // now if I was output the api date to another format
        // I have to change the formatter
        [formatter setDateFormat:@"dd/M/yyyy"];
        NSString *currentDate = [formatter stringFromDate:apiDate];

        NSLog(@"Current Date: %@", currentDate);
    }
    return 0;
}

I used the wrong formatter for milliseconds. It's capital S's. — Black Frog, Apr 19 '15 at 16:48
Yes just like I wrote in my answer. If it worked out for you @IbrahimAzharArmar I would appreciate marking the answer as accepted since this way people who face the same problem can find the way to go easily. But I mean you have 8000 reputation points I think you know that by yourself, just a reminder. — dehlen, Apr 19 '15 at 17:11

score 1 · Answer 2 · answered Apr 19 '15 at 16:40

Just want to add to Black Frog's answer: As he stated you need different formatters for reading/writing.

However the right format should be :

[formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSSSSS"];

According to the apple documentation fractional seconds should be formatted with 'S'.

See here: NSDateFormat

Also here is an example to accomplish your task:

    NSString *datevalue = @"2015-04-18 06:08:28.000000";
    NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
    [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss.SSSSSS"];
    NSDate *date =  [formatter dateFromString:datevalue];
    [formatter setDateFormat:@"dd/MM/yyyy"];
    NSString *currentDate = [formatter stringFromDate:date];

    NSLog(@"%@",date);
    NSLog(@"%@",currentDate);

Rob · Accepted Answer · 2015-04-19T18:30:31.590

You should use the yyyy-MM-dd HH:mm:ss.SSSSSSS format string for the date formatter converting the API date into a NSDate object, as discussed by the others. But, you also want to consider the timeZone and locale properties of this formatter.

Usually RFC 3339 dates are exchanged in GMT. Confirm this with your API, but it's generally GMT/UTC/Zulu. If so, you will probably also want to explicitly set the timezone:
```
formatter.timeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
```
But confirm what timezone the API expects.

A more subtle issue is the handling users with non-Gregorian calendars

formatter.locale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US_POSIX"];

For more information, see Apple Technical Q&A 1480.

Clearly, these dateFormat, timeZone, and locale properties are simply for converting the API date string into a NSDate object. When then outputting the date for the end user, you would use a separate formatter, defaulting to the standard timeZone and locale properties and use whatever dateFormat string you want for the output. (Frankly, I wouldn't generally advise using dateFormat string for user output formatters, but rather just use the appropriate values for the dateStyle and timeStyle properties.)

Format RFC3339 dates

3 Answers3