JSON date to NSDate Issue - objective-c

Question

I have a date string in JSON format, it looks like this:
2013-05-22T10:54:40.437
And I'm trying to convert it to NSDate.
- (NSString *)dateFromString:(NSString *)datestring{
// Convert string to date object
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"yyyy'-'MM'-'dd'T'HH':'mm':'ss"];
NSDate *date = [dateFormat dateFromString:datestring];
//date is nil here.
NSDateFormatter *newDateFormatter = [[NSDateFormatter alloc]init];
[newDateFormatter setDateFormat:#"MM/dd/yyyy"];
NSString *newString = [newDateFormatter stringFromDate:date];
NSLog(#"Date -- %#",datestring);
return newString;
}
But date is nil after dateFromString. Does anyone know what I did wrong here?
Thanks!

Answer 1

Use this date format:
yyyy-MM-dd'T'HH:mm:ss.SSS
Your code with little modification:
NSDateFormatter *dateFormat = [[NSDateFormatter alloc] init];
[dateFormat setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSS"];
NSDate *date = [dateFormat dateFromString:datestring];
NSDateFormatter *newDateFormatter = [[NSDateFormatter alloc]init];
[newDateFormatter setDateFormat:#"MM/dd/yyyy"];
NSString *newString = [newDateFormatter stringFromDate:date];
NSLog(#"Date: %#, formatted date: %#", date, newString);
gives me this output:
Date: 2013-05-22 08:54:40 +0000, formatted date: 05/22/2013
Edit: how "ikinci viking" pointed out in comment, escaping the dashes is unnecessary. Escaping removed from the code
Update for iOS 11+
ISO8601DateFormatter is the recommended way to parse internet date on iOS 10+.
However it has few issues preventing it from usage with the specific format from the question:
Milliseconds are supported only on iOS 11+
It does not work for dates without timezone (the case in question). Date string must contain timezone part (e.g. +00:00 or Z for "Zulu time" UTC)
If date strings contains both milliseconds and timezone (e.g. 2018-09-07T14:04:13.143Z), it can be used as follows (Swift example):
let isoDateFormatter = ISO8601DateFormatter()
isoDateFormatter.formatOptions = [.withInternetDateTime, .withFractionalSeconds]

Answer 2

Your date format is incorrect. It should be:
[dateFormat setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss:SSS"];
The three capital 'S' means it will take the fractional part to 3 digits. Adjust it as you will.

Answer 3

If your date format is "2014-02-25T13:05:10+00:00" then,
your code should be like this....
NSURL *url = [NSURL URLWithString:#"your URL"];
NSString *str = [[NSString alloc] initWithContentsOfURL:url usedEncoding:Nil error:Nil];
NSDateFormatter *dateFor = [[NSDateFormatter alloc] init];
[dateFor setDateFormat:**#"yyyy-MM-dd'T'HH:mm:ss'+'SS:SS"**];
NSDate *yourDate = [dateFor dateFromString:str];
NSLog(#"Your Date: %#",yourDate);

Answer 4

-(void)viewDidLoad {
self.date = [dateForRFC3339DateTimeString:#"2015-01-18T01:00:00.000Z"];
}
-(NSDate *)dateForRFC3339DateTimeString:(NSString *)rfc3339DateTimeString {
NSDateFormatter *rfc3339DateFormatter = [[NSDateFormatter alloc] init];
[rfc3339DateFormatter setDateFormat:#"yyyy'-'MM'-'dd'T'HH':'mm':'ss'.'SSS'Z'"];
[rfc3339DateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
// Convert the RFC 3339 date time string to a NSDate.
NSDate *result = [rfc3339DateFormatter dateFromString:rfc3339DateTimeString];
return result;
}