CODEWITHSUNDEEP
iosobjective-cdstnstimezone
UdayM
UdayM

Reputation: 1783

NSTimeZone isDaylightSavingTime giving wrong value

Currently GMT-0700(US/pacific) is already in day-light-saving

But I am getting "NO" from NSTimeZone

NSTimeZone *timeZone = [NSTimeZone timeZoneForSecondsFromGMT:secondsFromGMT]; //Getting timezone as GMT-0700 
BOOL isDaylightSavingTime = [timeZone isDaylightSavingTime]; //getting boolean value as NO

How to fix this issue?

REQUIREMENT :I want to know ,my receiver is using dayLightSavingTime or not.i will get only receiver offset value.I have to support different timezones()..What is the best approach to do this

Upvotes: 0

Views: 666

Answers (3)

Tom Harrington
Tom Harrington

Reputation: 70956

Other answers mentioning timeZoneWithName are correct but there's one more detail I don't think has been mentioned. The reason that timeZoneForSecondsFromGMT doesn't work is that GMT does not have daylight savings time (or summer time, as it's more sensibly called in some other countries). GMT doesn't jump forward or back; it always moves ahead by one second per second. Since you ask for a fixed number of seconds from GMT, the result also does not have GMT. If it gave you a time zone that observed daylight saving time, the number of seconds from GMT would have to change twice a year. But since you asked for a fixed number of seconds, you get a result that doesn't do that, and never reports daylight saving time in effect.

Upvotes: 0

vadian
vadian

Reputation: 285092

timeZoneForSecondsFromGMT is not specific enough.

The most accurate way is to create the time zone with the (full) region name: 

NSTimeZone* timeZone = [NSTimeZone timeZoneWithName:@"America/Los_Angeles"];

Upvotes: 2

Sergey
Sergey

Reputation: 1617

This is not a wrong value. You get timezone GMT-0700 but this is not a Pacific timezone. To create pacific timezone you need:

timeZone = [NSTimeZone timeZoneWithName:@"PST"];

This is short description from apple documentation:

+ (instancetype)timeZoneForSecondsFromGMT:(NSInteger)seconds;

Description Returns a time zone object offset from Greenwich Mean Time by a given number of seconds. The name of the new time zone is GMT +/– the offset, in hours and minutes. Time zones created with this method never have daylight savings, and the offset is constant no matter the date.

Upvotes: 1

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