trying to use a uidatepicker. have a method that fires when the value of the datepicker changes. it passes the date value, but when i try and take that date, my days portion is acting goofy. it returns the number of days since the beginning of the year, not the actual month day. so say February 3rd, instead of 3, i get 34.
-(IBAction)datePickerValueChanged: (id)sender;
{
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"YYYY-MM-DD"];
self.date = [dateFormatter stringFromDate:[sender date]];
NSLog(#"date: %#", [dateFormatter stringFromDate:[sender date]]);
[dateFormatter release];
}
for april 12th, i get:
2011-10-27 14:22:41.939 Satshot[12789:40b] date02: 2011-04-102
i'm guessing my dateformatter is causing it, but i don't understand why.
You are using the wrong format specifier. You need "yyyy-MM-dd"
http://unicode.org/reports/tr35/tr35-10.html#Date_Format_Patterns
Update, YYYY and DD are both wrong. Thanks #jrturton.
From the Data Formatting Guide:
It uses yyyy to specify the year component. A common mistake is to use
YYYY. yyyy specifies the calendar year whereas YYYY specifies the year
(of "Week of Year"), used in the ISO year-week calendar. In most
cases, yyyy and YYYY yield the same number, however they may be
different. Typically you should use the calendar year.
In addition, DD should be dd.
Though why not just use the date to hold your value internally?
Also, note that creating a date formatter is an expensive exercise, valueChanged on a picker view could be called tens of times a second as the user scrolls through. If you must use a formatter, cache it.
Related
My date is in the format
2013-07-16T07:40:36.939-04:00
When I convert it into a NSDate
the date is in the format IST or GMT +5:30 as I am in India. How should I make it use -4:00 as the timezone and display EST or PDT as per the number. if I use zzz, it returns GTM+5:30 and zzzz returns Indian Standard Time. This is my way
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MM-dd'T'HH:mm:ss.SSSzzz"];
NSDate *date = [dateFormatter dateFromString:strDate];
You need to set the formatted locale to en_US_POSIX to force it to use the supplied timezone instead of the system timezone:
[dateFormatter setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US_POSIX"]];
You're parsing the date string correctly (in iOS 6 and later; this is not date format recognized in iOS 5 which recognizes -0400 or GMT-04:00, but not -04:00). Unfortunately, NSDate objects do not have a "time zone", so that information is not captured by the NSDateFormatter.
If you really want to capture the original timezone, I think you may have to manually parse the string for those last few characters (the -04:00), determine the timezone offset from that, and store this in a separate field and when outputting the date, use this separate time zone offset to set the timeZone property of your date formatter accordingly. Or if you really want to represent the original date, you could reformat this ISO8601 date string as human-friendly string and keep this pretty string (as well as the NSDate object, presumably).
BTW, splitting hairs, but you might want to be wary about assuming that -04:00 will represent EDT because (a) it depends upon the time of the year; and (b) there are other timezones that are also -04:00 (e.g. there are a bunch of South American timezones that are also -04:00).
Generally apps avoid this problem altogether by (a) converting the date strings to NSDate objects; and (b) output these NSDate objects using the timezone and locale of the device that the app is running on.
This question already has answers here:
Get NSDate from NSDate adjusted with timezone
(2 answers)
Closed 9 years ago.
I am trying to use NSDateFormatter in my app which takes a date string and formats it to an NSDate so that I can do Date Comparisons, however I am finding when I use dateFromString and format it the date is losing one day.
NSString *dateString = #"02-06-2012";
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"dd-MM-yyyy"];
NSDate *dateFromString = [[NSDate alloc] init];
dateFromString = [dateFormatter dateFromString:dateString];
NSLog(#"My Date = %#", dateFromString);
[dateFormatter release];
This outputs to the console:
My Date = 2012-06-01 23:00:00 +0000
Try adding this lines to your code,
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:#"GMT+0:00"]];
or
[dateFormatter setTimeZone:[NSTimeZone timeZoneWithName:#"GMT"]];
SWIFT update :
Code from quetion,
let dateString = "02-06-2012"
var dateFormatter = NSDateFormatter()
dateFormatter.dateFormat = "dd-MM-yyyy"
var dateFromString : NSDate = dateFormatter.dateFromString(dateString)!
println("My Date \(dateFromString)")
And Solution ,
dateFormatter.timeZone = NSTimeZone(name: "GMT")
OR
dateFormatter.timeZone = NSTimeZone(abbreviation: "GMT+0:00")
I don't believe that Dhruv's answer is correct. In fact, it's not clear there's any problem at all. You just seem to have an incorrect expectation of what should happen and/or interpretation of what's happening.
NSDate represents a moment in time. This moment does not have one unique name. It will be known by different names in different places and under different naming systems (time zones, calendars). NSDate doesn't deal with any of this, except lamely in its -description method, where it has to produce a string representation of that moment.
Second, a string like "02-06-2012" doesn't specify a precise moment in time. First of all, it's just a date with no time information, so NSDateFormatter just defaults to the first moment for that date. Second, it doesn't specify the time zone. The first moment of the calendar day is a different moment in each time zone. Unless you specify a time zone with -setTimeZone: or the string itself carries time zone information, NSDateFormatter assumes that any date strings you ask it to parse are in the current time zone.
So, your dateFromString object represents the first moment of the specified date, 02-06-2012, in your time zone. I expect this is what you wanted. However, you then got confused by the way that NSDate describes itself when logged. As I said, NSDate has to pick some "name" (string representation) for the moment it represents and which name it picks is fairly arbitrary. These days it is picking the name that the moment is known by in UTC. I gather from the log output shown in your question that you are located at UTC+0100. So, the date may look like it's one day earlier but it really is the same moment you specified. In other words, "2012-06-01 23:00:00 +0000" and "2012-06-02 00:00:00 +0100" are two equivalent names for exactly the same moment in time. You just aren't used to seeing the first one and misinterpreted it.
The lesson is that you have to stop relying on NSDate's self-description to be in any particular time zone. Really, you have to not rely on anything about it, since it's not documented. In fact, the docs for -[NSDate description] state, "The representation is not guaranteed to remain constant across different releases of the operating system."
Dhruv's solution seems to help merely because it causes NSDateFormatter and -[NSDate description] to agree on the time zone. But that's unreliable. It wouldn't work on Snow Leopard, for example, because -[NSDate description] used the local time zone instead of UTC in that version of the frameworks.
More importantly, though, it alters the actual moment represented by the NSDate object you get from NSDateFormatter's interpretation of your date string. I suspect you really want that to have a specific meaning – you want the string to be interpreted as being in the local time zone – and his solution thwarts your intent.
tl;dr: you were getting the date you wanted all along; don't rely on -[NSDate description]; don't use Dhruv's solution
I am trying to format a date object and I am noticing on the string I am passing in; 6 hours is being added to my time. This seems to be associating my date time object to GMT.
My code:
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:#"yyyy-MM-dd h:mm:ss a"];
[formatter setTimeZone:[NSTimeZone systemTimeZone]];
NSDate *date = [formatter dateFromString:#"2012-02-01 03:38:12 AM"];
NSLog(#"%#", date);
The result is:
2012-02-01 09:38:12 +0000
I have tried this with and without the setTimeZone and it does not matter. Any ideas on why this is displaying as GMT time?
Thanks,
Flea
The date that your formatter creates is not associated with any timezone, but the description method of NSDate (which is what NSLog uses for the output) converts any date to UTC. You would have to use another (or the same) date formatter's stringFromDate: method to print it with a different time zone.
All NSDates are absolute times, meaning that 3:00 AM central time in the United States is 9 AM UTC. I suspect that your systemTimeZone is central time in the United States.
NSLog always shows times in UTC.
If you want to see, as a string, what the time is in your time zone, then you can use the same date formatter stringFromDate: method, and make the you set the time zone of the date formatter to that time zone.
NSLog date formatting is an annoyance because it leads to the kind of confusion you are experiencing.
How can I customize a UIDatePicker to only show the month and year? There's an existing mode that shows the day, month, and year, but I'd like to get rid of the day portion.
Simply put, you can't. UIDatePicker does not have any API for only showing years and months.
You therefore have 3 possible recourses:
Make your own out of a UIPickerView
Use a UIDatePicker in Date mode and just ignore the day portion
File a bug asking for this capability and hope it gets added at some point
I vote for #1 and #3.
It is not Possible to customize the date picker like you need in the nib file.You can set the mode in nib to get only date or time or both.In this case you need to format your date to the required format using dateFormatter.For this you can set the format to "yyyy-MMM",which will returns you the year and month.
eg:
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"yyyy-MMM"];
NSString *formattedDate = [dateFormatter stringFromDate:date];
[dateFormatter release];
Before Xcode 4 I used to use NSDate initFromString but it is now deprecated and produces errors in Xcode 4.2. So I jumped over to using NSDateFormatter dateFromString but ran into an issue in a method I call that gets a sunrise date from string and a sunset date from string to determine if it is day or night (so same method). The first call works fine, but the second call returns nil. I decided to see if it was repeatable so I created the following simple method and dumped it into another project in an innocuous place:
- (void)testDateFormatter
{
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat: #"yyyy-MM-dd hh:mm:ss Z"];
NSString *srDateTimeString = #"2011-11-09 07:08:00 -0800";
NSString *ssDateTimeString = #"2011-11-09 17:08:00 -0800";
NSDate *sunriseDateTime = [formatter dateFromString: srDateTimeString];
NSDate *sunsetDateTime = [formatter dateFromString: ssDateTimeString];
return;
}
The first call returns the correct date. The second call returns nil. I have tried several variations (such as creating two separate NSDateFormatters, preinitializing the dates, preinitializing the dates to the current time and then reassigning) but none do the expected thing.
Does anyone know what is going on here? Since I hadn't found any reference to this error anywhere I submitted it to Apple (bug #10420498).
Jack
In the second string, the hour is 17 (24-hour format) but the format string uses hh (lowercase) which is for 12-hour format.
Change the format string to yyyy-MM-dd HH:mm:ss Z.
In the documentation, see Date Formatters which contains a link to the Unicode Date Format Patterns listing each format specifier.