Date from String returns null value

I have the following NSDate 01 Jan 2015 which I want to convert to a string. The string reportArtDate has the string 01 Jan 2015.

My code is:

NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:@"dd MMM yyyy"];
[dateFormatter setTimeZone:[NSTimeZone systemTimeZone]];
NSDate *dateFromString = [[NSDate alloc] init];
dateFromString = [dateFormatter dateFromString:reportArtDate];

The above is fine on an iPhone 4, but it fails on an iPhone 5 with version 8.1.3.

But the dateFromString is always null.

Any ideas very welcome.

Thanks a lot.

Edit The problem arises if the users locale is not en_EN. In this case, the user had es_ES locale. So I set the locale before the format set and the NSString was translated to NSDate with success.

The code that works is as follows:

    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]
    NSDate *dateFromString = [[NSDate alloc] init];
    [dateFormatter setLocale:[NSLocale localeWithLocaleIdentifier:@"en_EN"]];
    [dateFormatter setDateFormat:@"dd MMM yyyy"];
    dateFromString = [dateFormatter dateFromString:reportArtDate];

In case it helps others.