I am trying to convert nsstring to nsdate and then to the systemtimezone. Is my code right? Any help appreciated.
NSString *str=@"2012-01-15 06:27:42";
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[NSDateFormatter setDefaultFormatterBehavior:NSDateFormatterBehaviorDefault];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *dateFromString = [dateFormatter dateFromString:str];
NSDate* sourceDate = dateFromString;
NSTimeZone* sourceTimeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT-07:00"];
NSTimeZone* destinationTimeZone = [NSTimeZone systemTimeZone];
NSInteger sourceGMTOffset = [sourceTimeZone secondsFromGMTForDate:sourceDate];
NSInteger destinationGMTOffset = [destinationTimeZone secondsFromGMTForDate:sourceDate];
NSTimeInterval interval = destinationGMTOffset - sourceGMTOffset;
NSDate* destinationDate = [[[NSDate alloc] initWithTimeInterval:interval sinceDate:sourceDate] autorelease];
bottomLabel2.text=[NSString stringWithFormat:@"- %@ -",destinationDate];
The code result is 2012-01-15 06:27:42 +0000 which is the same as the source!
I think I can see what the problem is here - it's this line:
NSTimeZone* sourceTimeZone = [NSTimeZone timeZoneWithAbbreviation:@"GMT-07:00"];
GMT-07:00 is not a valid abbreviation for this method. If you call [NSTimeZone abbreviationDictionary] you'll get a dictionary containing all available abbreviations. You need to use the actual abbreviation (eg, 'PST' for Pacific Standard Time), and not the format "GMT-07:00".
To save you time, here's the full list of supported abbreviations using NSTimeZone.
ADT = "America/Halifax";
AKDT = "America/Juneau";
AKST = "America/Juneau";
ART = "America/Argentina/Buenos_Aires";
AST = "America/Halifax";
BDT = "Asia/Dhaka";
BRST = "America/Sao_Paulo";
BRT = "America/Sao_Paulo";
BST = "Europe/London";
CAT = "Africa/Harare";
CDT = "America/Chicago";
CEST = "Europe/Paris";
CET = "Europe/Paris";
CLST = "America/Santiago";
CLT = "America/Santiago";
COT = "America/Bogota";
CST = "America/Chicago";
EAT = "Africa/Addis_Ababa";
EDT = "America/New_York";
EEST = "Europe/Istanbul";
EET = "Europe/Istanbul";
EST = "America/New_York";
GMT = GMT;
GST = "Asia/Dubai";
HKT = "Asia/Hong_Kong";
HST = "Pacific/Honolulu";
ICT = "Asia/Bangkok";
IRST = "Asia/Tehran";
IST = "Asia/Calcutta";
JST = "Asia/Tokyo";
KST = "Asia/Seoul";
MDT = "America/Denver";
MSD = "Europe/Moscow";
MSK = "Europe/Moscow";
MST = "America/Denver";
NZDT = "Pacific/Auckland";
NZST = "Pacific/Auckland";
PDT = "America/Los_Angeles";
PET = "America/Lima";
PHT = "Asia/Manila";
PKT = "Asia/Karachi";
PST = "America/Los_Angeles";
SGT = "Asia/Singapore";
UTC = UTC;
WAT = "Africa/Lagos";
WEST = "Europe/Lisbon";
WET = "Europe/Lisbon";
WIT = "Asia/Jakarta";
The list above of “supported" abbreviations is also an abbreviated list..
if you want to see a fairly complete list, here is some code to generate it:
(and a small part of the output below to show some that are not in the list above) unfortunately the OS will not use these extra zones) you’ll have to do a conversion to -0600 types
NSDate *myDate = [NSDate date];
NSDateFormatter *f = [[NSDateFormatter alloc] init];
[f setDateStyle:NSDateFormatterLongStyle];
[f setTimeStyle:NSDateFormatterLongStyle];
[f setDateFormat:@"ZZZ"];
NSArray *timeZoneNames = [NSTimeZone knownTimeZoneNames];
for (NSString *name1 in timeZoneNames)
{
NSTimeZone *tz = [NSTimeZone timeZoneWithName:name1];
[f setTimeZone:tz];
NSLog(@"%@ = \"%@\" = %d = %@", [tz abbreviation], name1, [tz secondsFromGMT], [f stringFromDate:myDate]);
}
2012-02-13 15:53:26.497 HelloWorld[23220:207] NZDT = "Pacific/Auckland" = 46800 = +1300
2012-02-13 15:53:26.498 HelloWorld[23220:207] CHADT = "Pacific/Chatham" = 49500 = +1345
2012-02-13 15:53:26.508 HelloWorld[23220:207] CHUT = "Pacific/Chuuk" = 36000 = +1000
2012-02-13 15:53:26.509 HelloWorld[23220:207] EASST = "Pacific/Easter" = -18000 = -0500
2012-02-13 15:53:26.510 HelloWorld[23220:207] VUT = "Pacific/Efate" = 39600 = +1100
2012-02-13 15:53:26.511 HelloWorld[23220:207] PHOT = "Pacific/Enderbury" = 46800 = +1300
2012-02-13 15:53:26.512 HelloWorld[23220:207] TKT = "Pacific/Fakaofo" = -36000 = -1000
2012-02-13 15:53:26.513 HelloWorld[23220:207] FJT = "Pacific/Fiji" = 43200 = +1200
2012-02-13 15:53:26.514 HelloWorld[23220:207] TVT = "Pacific/Funafuti" = 43200 = +1200
2012-02-13 15:53:26.515 HelloWorld[23220:207] GALT = "Pacific/Galapagos" = -21600 = -0600
2012-02-13 15:53:26.516 HelloWorld[23220:207] GAMT = "Pacific/Gambier" = -32400 = -0900
2012-02-13 15:53:26.518 HelloWorld[23220:207] SBT = "Pacific/Guadalcanal" = 39600 = +1100
2012-02-13 15:53:26.518 HelloWorld[23220:207] ChST = "Pacific/Guam" = 36000 = +1000
2012-02-13 15:53:26.520 HelloWorld[23220:207] HST = "Pacific/Honolulu" = -36000 = -1000
2012-02-13 15:53:26.521 HelloWorld[23220:207] HST = "Pacific/Johnston" = -36000 = -1000
2012-02-13 15:53:26.522 HelloWorld[23220:207] LINT = "Pacific/Kiritimati" = 50400 = +1400
2012-02-13 15:53:26.523 HelloWorld[23220:207] KOST = "Pacific/Kosrae" = 39600 = +1100
2012-02-13 15:53:26.524 HelloWorld[23220:207] MHT = "Pacific/Kwajalein" = 43200 = +1200
2012-02-13 15:53:26.526 HelloWorld[23220:207] MHT = "Pacific/Majuro" = 43200 = +1200
2012-02-13 15:53:26.527 HelloWorld[23220:207] MART = "Pacific/Marquesas" = -34200 = -0930
2012-02-13 15:53:26.528 HelloWorld[23220:207] SST = "Pacific/Midway" = -39600 = -1100
2012-02-13 15:53:26.529 HelloWorld[23220:207] NRT = "Pacific/Nauru" = 43200 = +1200
2012-02-13 15:53:26.530 HelloWorld[23220:207] NUT = "Pacific/Niue" = -39600 = -1100
2012-02-13 15:53:26.531 HelloWorld[23220:207] NFT = "Pacific/Norfolk" = 41400 = +1130
2012-02-13 15:53:26.564 HelloWorld[23220:207] NCT = "Pacific/Noumea" = 39600 = +1100
2012-02-13 15:53:26.565 HelloWorld[23220:207] SST = "Pacific/Pago_Pago" = -39600 = -1100
2012-02-13 15:53:26.566 HelloWorld[23220:207] PWT = "Pacific/Palau" = 32400 = +0900
2012-02-13 15:53:26.567 HelloWorld[23220:207] PNT = "Pacific/Pitcairn" = -28800 = -0800
2012-02-13 15:53:26.570 HelloWorld[23220:207] PONT = "Pacific/Pohnpei" = 39600 = +1100
2012-02-13 15:53:26.571 HelloWorld[23220:207] PONT = "Pacific/Ponape" = 39600 = +1100
2012-02-13 15:53:26.572 HelloWorld[23220:207] PGT = "Pacific/Port_Moresby" = 36000 = +1000
2012-02-13 15:53:26.574 HelloWorld[23220:207] CKT = "Pacific/Rarotonga" = -36000 = -1000
2012-02-13 15:53:26.575 HelloWorld[23220:207] ChST = "Pacific/Saipan" = 36000 = +1000
2012-02-13 15:53:26.576 HelloWorld[23220:207] TAHT = "Pacific/Tahiti" = -36000 = -1000
2012-02-13 15:53:26.578 HelloWorld[23220:207] GILT = "Pacific/Tarawa" = 43200 = +1200
2012-02-13 15:53:26.579 HelloWorld[23220:207] TOT = "Pacific/Tongatapu" = 46800 = +1300
2012-02-13 15:53:26.580 HelloWorld[23220:207] CHUT = "Pacific/Truk" = 36000 = +1000
2012-02-13 15:53:26.582 HelloWorld[23220:207] WAKT = "Pacific/Wake" = 43200 = +1200
2012-02-13 15:53:26.583 HelloWorld[23220:207] WFT = "Pacific/Wallis" = 43200 = +1200
来源：https://stackoverflow.com/questions/8871727/gmt-timezone-conversion-in-objective-c