I have a TimeZone as NSString value given as "GMT-09:00".
All I want is to setup my NSTimeZone with this format. I tried but wasn't able to do this. This time may vary every time so i can't set it as static in the method
eg. i can't do this -- timeZoneForSecondsFromGMT:(-9*3600).
Also, can I convert the above format (GMT-09:00) into number of seconds anyhow??
EDIT : I just want to set the time zone to a specific GMT format. It could be anything, GMT-09:00, GMT+05:30, etc.
If it was a static value I could have used the below method for NSTimeZone.
[formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:(-9*3600)]];
But the value "GMT-09:00" is an NSString. So everytime, I would have to break the string and get the values for Hours and minutes. Is there an easier way?????
Thanks for the help!
have you tried something like this?
NSString *tzStr = #"GMT-09:00";
NSTimeZone *tz = [[NSTimeZone alloc] initWithName:tzStr];
NSLog(#"Tz: %#", tz);
NSLog(#"Offset: %d", [tz secondsFromGMT]);
// Tz: GMT-0900 (GMT-09:00) offset -32400
// Offset: -32400
works with #"GMT+5:30" too.
// Tz: GMT+0530 (GMT+05:30) offset 19800
and then just use [formatter setTimeZone:tz];
this one is helpful to you. optimized help
float offsetSecond = ([[NSTimeZone systemTimeZone] secondsFromGMT] / 3600.0);
Related
Below is the string of time stamp which is returned by some server
dateFromServer = 2013-07-08 16:45:03Z
I am doing the following to convert it to an NSDate
NSDateFormatter *format = [[NSDateFormatter alloc] init];
[format setDateFormat:#"yyyy'-'MM'-'dd' 'HH':'mm':'ss'Z'"];
NSTimeZone *destinationTimeZone = [NSTimeZone systemTimeZone];
[format setTimeZone:destinationTimeZone];
dateFromServer = [dateFromServer stringByReplacingOccurrencesOfString:#"T" withString:#" "];
NSDate *oldTime = [format dateFromString:dateFromServer];
and I am getting
oldTime is 2013-07-08 20:45:03 +0000
It looks like +4 is added to the original time stamp
Why does it do that, and how do I avoid this situation?
The NSDate object doesn't preserve the timezone. Instead, when printing the date (I assume through a NSLog(#"%#", oldTime);) it will use the current timezone. If your system is set to GMT (+0000) then it will print like that.
The date is still correct, and if you force it to print with the correct time zone it will be correct.
I personally do not know objective C but I do know the point of the problem. I'll try to guess along with the syntax.
When you receive 2013-07-08 16:45:03Z the Z means UTC, or GMT+/-0000.
You are parsing it as a local timezone, or GMT-0400.
You then reemit it as reconverted into UTC with a 4 hour overcompensation.
To fix this, change:
NSTimeZone *destinationTimeZone = [NSTimeZone systemTimeZone];
to
NSTimeZone *destinationTimeZone = [NSTimeZone timeZoneForSecondsFromGMT:0];
Honestly, I'm not sure if you need to do any wrapping for the 0 to act as an NSInteger but that's what you need.
You may have been intermittently missing this bug as a failure to determine time would have fallen back to the desired effect.
Out of curiosity, could someone comment as to whether my code is at least partially correct?
I get a unix timestamp from the database and I am trying to create a human readable date from it. I am using this way
long t1=[time longLongValue];
NSDate* date=[NSDate dateWithTimeIntervalSince1970:t1];
where time is the timestamp. When I print date I get
1956-02-18 19:04:01 +0000
instead of
2013-01-02 12:31:03 +0000
The timestamp was 1356765933449
It is a matter of integer overflow, as Boris correctly pointed out in his answer.
I don't know what your time object is, but instead of a signed long int use a NSTimeInterval.
On iOS NSTimeInterval is currently defined as
typedef double NSTimeInterval;
but you shouldn't care too much about that. Sticking with type synonyms will protect you in case Apple decides to change the underlying definition to something else.
That said you should change your code to something like
NSTimeInterval epoch = [time doubleValue];
NSDate * date = [NSDate dateWithTimeIntervalSince1970:epoch];
Concerning the code maintainability issue I described before, here you are explicitly using a doubleValue (you don't have many options), but the good thing is that if Apple changes the NSTimeInterval definition to something not compatible with a double assignment, the compiler will let you know.
Try this
- (NSString *) getDateFromUnixFormat:(NSString *)unixFormat
{
NSDate *date = [NSDate dateWithTimeIntervalSince1970:[unixFormat intValue]];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init];
[dateFormatter setDateFormat:#"MMM dd, yyyy-h:mm"];
[dateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
//NSDate *date = [dateFormatter dateFromString:publicationDate];
NSString *dte=[dateFormatter stringFromDate:date];
[dateFormatter release];
return dte;
}
The Unix timestamp has only 32 Bits available.
Because they use a signed int, they count the seconds from 1.1.1970. A 32 Bit signed int can only hold values up to 2147483647, where as you want it to be 1356765933449. That causes an overflow, and that causes your date to be invalid.
This is also known as the Year 2038 Problem, because 2147483647 (max value) will be hit on 03:14:07 UTC on Tuesday, 19 January 2038.
Then format the date using nsdateformatter. Details guide.
https://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Classes/NSDateFormatter_Class/Reference/Reference.html
I have an array which contains time in HH:mm:ss format.
I want to convert this into epoch time. To convert a particular time into epoch, date along with time should be passed.
I want to pass today's date along with the time from array.
For example 09:15:30 (date 22/12/2011) which is a string, should be converted into 1324525530000 (corresponding epoch value)
How should I convert this ??
Any help is appreciated.
Maybe you can get an idea looking at this snippet:
NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] initWithSafeDateFormat:#"dd/MM/yyyy HH:mm:ss"];
NSDate *date = [dateFormatter dateFromString:dateString];
NSTimeInterval epoch = [date timeIntervalSince1970];
Anyway you can have a look to NSDateFormatter and NSDate in the reference docs.
That looks like an epoch time in milliseconds - as far as I know it's supposed to be in seconds.
You can use NSDateFormatter to parse a string and convert it to a NSDate. This date can then return the seconds since 1970. If you really need it, simply multiply this by 1000.
I want to calculate time span for twitter and facebook.
For twitter:-Tue Jul 19 11:08:46 +0000 2011
for facebook:-2011-07-18T15:25:09+0000
I want to convert it in to like,1 hrs ago,60 min ago,2 mint ago etc.
And how to compare these time values for Time sorting.
Kindly Provide any sample code or Any class reference link,So that i can do that.
I am in the process of doing something similar.
I would first convert the time given by Twitter and Facebook into a NSDate using NSDateFormatter's setDateFormat function. Then you can compare by using NSDate's timeSinceNow function.
In the case of Twitter, it might look like this…
NSDateFormatter *dateFM = [[NSDateFormatter alloc] init];
[dateFM setDateFormat:#"EEE MMM dd HH:mm:ss ZZZZ yyyy"]; //set the format that matches Twitter's result…
[dateFM setLocale:[[NSLocale alloc] initWithLocaleIdentifier:#"en_US"]];
[dateFM setTimeZone:[NSTimeZone timeZoneWithName:#"UTC"]];
NSDate *twitterDate = [dateFM dateFromString:CTADateString];
float secondsOfTwitterDateSinceNow = [twitterDate timeIntervalSinceNow];
The result (secondsOfTwitterDateSinceNow) is the number of seconds elapsed since now which you can divide however you want (/60 = minutes, ect…)
My class needs two properties: startTime and endTime. What is the best class to use? I know there is NSDate, but I only need to store a specific time (something in between 00:00-23:59), I don't need a date. What is the most elegant solution here?
NSTimeInterval is probably good enough for this.
It stores a time value in seconds as a double.
Eg. 5 mins = 300.0
I believe the most elegant solution, and what you want, is NSTimeInterval, that is the primitive type that NSDate is built on top.
NSTimeInterval is a typedef for double, and is a measurement of time in seconds. This primitive time type do not have any concept of a reference date. What NSDate do is to add this concept of reference date and anchor the 0.0 time at 1 January 2001 GMT. There is nothing that stops you from inventing your own reference date or anchor, like for example "midnight of whatever day there is".
What you can do is to add two properties of the NSTimeInterval either as startTime and endTime and let them both use midnight as the reference. Or you could skip endTime and go for a startTime and duration combo.
There's NSDateComponents, which "can also be used to specify a duration of time, for example, 5 hours and 16 minutes."
The NSDate class is similar to the DateTime class in C#: both hold a date and time, but they can be independent of each other. In Cocoa, you would compare two NSDate classes:
//Create NSDate objects in the time format
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateFormat:#"HH:mm:ss"];
NSString *startTimeString = #"00:00:00"; //0 seconds
NSString *endTimeString = #"00:00:52"; //52 seconds
NSDate *startTime = [dateFormatter dateFromString:startTimeString];
NSDate *endTime = [dateFormatter dateFromString:endTimeString];
//Compare the time
BOOL date1before2 = [startTime compare:endTime] == NSOrderedAscending;