I'm trying to create an NSDate with dateWithTimeIntervalSince1970 but I keep getting an NSInvalidArgumentException. I can't figure out what's wrong with my syntax:
// [mutableItem valueForKey:#"date"] is a string which represents an integer of milliseconds
NSDate *dateObject = [NSDate dateWithTimeIntervalSince1970:([[mutableItem valueForKey:#"date"] longLongValue]/1000)];
Can anyone see what's wrong with this?
If you divide by 1000 you divide it with an integer. If you divide by 1000. (DOT) then it might work.
dateWithTimeIntervalSince1970: requires an NSTimeInterval which is a double.
Can you check your mutableItem value?
Here's my working example:
NSString *mutableItem = #"1344981600000";
NSDate *dateObject = [NSDate dateWithTimeIntervalSince1970:([mutableItem longLongValue]/1000)];
//dateObject = 2012-08-14 22:00:00 +0000
Related
I am trying to get a NSDate object from a UTC time string. The example of the time string is this:
2016-07-29T11:43:55+02:00
I am usingNSDateFormatter and set the formate as: yyyy-MM-dd'T'HH:mm:ss
However this gives me the take with incorrect time zone. So the above date will be: 2016-07-29T09:43:55+00:00
How do I keep the time zone aspect as well?
I did try adding a 'Z' to the end of the formatter but that just returns a nil date.
Try this
NSDateFormatter *userFormatter = [[NSDateFormatter alloc] init];
[userFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSSZ"];
NSLocale *posix = [[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"];
[userFormatter setLocale:posix];
NSString *dateConverted = [userFormatter stringFromDate:theDate];
Thanks to all that help. Solved the issue. The time on my iOS Simulator was correct. However when I called [NSDate date]; it show'd me a time two hours before local time. Hence the 'errors' I was seeing in the formatting of NSDate.
Use NSISO8601DateFormatter if targeting iOS 10 and above. https://developer.apple.com/documentation/foundation/nsiso8601dateformatter
I am trying to get the epoch time for a date (2016-03-31T17:58:30.812Z) and I'm having trouble converting. Here is what I have tried:
NSDateFormatter* df = [NSDateFormatter new];
NSDate* tokenCreated = [NSDate new];
[df setDateFormat:#"yyyy-MM-dd'T'HH:mm:sssZ"];
tokenCreated = [df dateFromString:#"2016-03-31T17:58:30.812Z"];
NSTimeInterval timeTokenCreated = [tokenCreated timeIntervalSince1970];
NSLog(#"TIME TOKEN::::%f", timeTokenCreated);
What is happening is that tokenCreated is being set to nil, and I'm unable to convert. Can someone please point me in the right direction and tell me where I'm going wrong?
What is happening is that tokenCreated is being set to nil
Because your date format doesn't match your string. For example, your format fails to distinguish between the seconds and the fractional seconds. You would need this:
#"yyyy-MM-dd'T'HH:mm:ss.SSSZ"
Below is a string represented a date
NSString *dateStr = #"2011-07-06";
And when I am trying to convert it to NSDate by doing :
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:#"yyyy-MM-dd"];
NSDate *tmp = [format dateFromString:dateStr];
NSLog(#"tmp is %#",[tmp description]);
What I am getting from the console is
tmp is 2011-07-06 04:00:00 +0000
I dont understand why I am getting extra info :04:00:00 +0000 for the result
Please help if you experienced it before
Your code
NSString *dateStr = #"2011-07-06";
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:#"yyyy-MM-dd"];
NSDate *tmp = [format dateFromString:dateStr]
will result in a NSDate object, that represents your local time at 0:00 — the beginning of the day.
but if you print a plain date object, it will result in a string that represents the time in GMT timezone, as internally all dates are normalized to that timezone.
As your string is 4 hours ahead, we can tell, that you most likely are in East Europe, maybe Moscow.
So if you want to see the string in your timezone, you need to use a NSDateFormatter to create it from the date object.
NSLog(#"tmp is %#",[formatter stringFromDate:tmp]);
to check, if it is correct, what I said, change the format to contain the time components.
formatter.format = [#"yyyy-MM-dd HH:mm"];
NSLog(#"tmp is %#",[formatter stringFromDate:tmp]);
The formatter will also take "oddities" like Leap Day, Leap Month (yes — those exits), Daylight Saving Times, Leap Seconds … in account — accordantly to the current calendar.
A great WWDC 2011 Video: Performing Calendar Calculations — a must-see for every cocoa developer.
BTW: to print a object with NSLog you dont need to call -description on it to pass in a string. NSLog will do this internally.
NSLog(#"tmp is %#", tmp);
is just fine.
The answer is simple, NSLog just converts the NSDate to a NSString, using its formatter with GMT (zero) timezone.
Your formatter is by default set to your default time zone, which is probably -4:00. When you print it out, NSLog converts it to 0:00, adding 4 hours.
In general, it's unsafe to parse dates without specifying their timezone.
Q1. NSDate *now = [NSDate date];
NSLog(#"Current date:%#",now);
The time shown is 4 hours ahead of the system time. I am wondering why is it so and how can I correct it?
Q2.. In C/C++, strings are treated as an array of characters. Is it the case in Objective-C also?
NSDate *now = [NSDate date];
NSLog(#"Current date:%#",now);
it's "now" not "date".
A1: NSLog(#"%#", now) is effectively the same as NSLog(#"%#", [now description]). The NSDate object doesn't care what the timezone is, so its description method will just give you the time in UTC. If you need to format with the right timezone and locale, you'll need to use an NSDateFormatter object to convert it to a nicely formatted string first.
A2: Yes and no, but mostly no. You can do this:
char *cString = "I am a C string";
to create a C string, which you can treat exactly as you would in C. That's something you very rarely see in Objective-C, though, except when it's absolutely necessary. The "normal" way to use strings is with instances of NSString or NSMutableString, which are fully-fledged objects:
NSString *normalString = #"I'm above all that."; (note the # symbol)
I'm using the JSON library from Stig Brautaset(http://code.google.com/p/json-framework) and I need to serialize an NSDate. I was considering converting it into a string before JSONifying it, however, I ran into this weird behavior:
Why aren't these NSDates considered equal?
NSDate *d = [[NSDate alloc] init];
NSDate *dd = [NSDate dateWithString:[d description]];
NSLog(#"%#", d);
NSLog(#"%#", dd);
if( [d isEqualToDate:dd] ){
NSLog(#"Yay!");
}
When you describe the original date object you lose some sub-second precision from the original object — in other words, -description shaves off fractional seconds, and returns
A string representation of the receiver in the international format YYYY-MM-DD HH:MM:SS ±HHMM, where ±HHMM represents the time zone offset in hours and minutes from GMT
When you create a new date object based on the description, you get it in whole seconds because the string is only precise to a whole second. So -isEqualToDate: returns NO because there is a difference of a fraction of a second between your two date objects, which it's sensitive to.
This method detects sub-second differences between dates. If you want to compare dates with a less fine granularity, use timeIntervalSinceDate: to compare the two dates.
So you'd do something like this instead (NSTimeInterval measures in seconds):
if ([d timeIntervalSinceDate:dd] == 0) {
NSLog(#"Yay!");
}
isEqualToDate detects subseconds differences between dates, but the description method does not include subseconds.
Because they're not equivalent:
NSDate *d = [NSDate date];
NSDate *dd = [NSDate dateWithString:[d description]];
NSLog(#"%f", [d timeIntervalSinceReferenceDate]);
NSLog(#"%f", [dd timeIntervalSinceReferenceDate]);
Produces:
2011-04-28 11:58:11.873 EmptyFoundation[508:903] 325709891.867788
2011-04-28 11:58:11.874 EmptyFoundation[508:903] 325709891.000000
In other words, the +dateWithString: method does not maintain sub-second precision.