iOS：将UTC NSDate转换为本地时区

如何NSDate在目标C或/和Swift中将UTC转换为本地时区NSDate？

NSTimeInterval seconds; // assume this exists
NSDate* ts_utc = [NSDate dateWithTimeIntervalSince1970:seconds];

NSDateFormatter* df_utc = [[[NSDateFormatter alloc] init] autorelease];
[df_utc setTimeZone:[NSTimeZone timeZoneWithName:@"UTC"]];
[df_utc setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];

NSDateFormatter* df_local = [[[NSDateFormatter alloc] init] autorelease];
[df_local setTimeZone:[NSTimeZone timeZoneWithName:@"EST"]];
[df_local setDateFormat:@"yyyy.MM.dd G 'at' HH:mm:ss zzz"];

NSString* ts_utc_string = [df_utc stringFromDate:ts_utc];
NSString* ts_local_string = [df_local stringFromDate:ts_utc];

// you can also use NSDateFormatter dateFromString to go the opposite way

格式化字符串参数表：

https://waracle.com/iphone-nsdateformatter-date-formatting-table/

如果性能是重中之重，则可能需要考虑使用 strftime

https://developer.apple.com/legacy/library/documentation/Darwin/Reference/ManPages/man3/strftime.3.html

编辑当我写这篇文章时，我不知道我应该使用dateformatter，这可能是一个更好的方法，所以也请查看slf的答案。

我有一个Web服务，它以UTC返回日期。我toLocalTime习惯将其转换为本地时间，并toGlobalTime在需要时进行转换。

这是我从以下位置得到答案的地方：

https://agilewarrior.wordpress.com/2012/06/27/how-to-convert-nsdate-to-different-time-zones/

@implementation NSDate(Utils)

-(NSDate *) toLocalTime
{
  NSTimeZone *tz = [NSTimeZone defaultTimeZone];
  NSInteger seconds = [tz secondsFromGMTForDate: self];
  return [NSDate dateWithTimeInterval: seconds sinceDate: self];
}

-(NSDate *) toGlobalTime
{
  NSTimeZone *tz = [NSTimeZone defaultTimeZone];
  NSInteger seconds = -[tz secondsFromGMTForDate: self];
  return [NSDate dateWithTimeInterval: seconds sinceDate: self];
}

@end

我找到的最简单的方法是：

NSDate *someDateInUTC = …;
NSTimeInterval timeZoneSeconds = [[NSTimeZone localTimeZone] secondsFromGMT];
NSDate *dateInLocalTimezone = [someDateInUTC dateByAddingTimeInterval:timeZoneSeconds];

Swift 3+：UTC到本地，本地到UTC

extension Date {

    // Convert UTC (or GMT) to local time
    func toLocalTime() -> Date {
        let timezone = TimeZone.current
        let seconds = TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }

    // Convert local time to UTC (or GMT)
    func toGlobalTime() -> Date {
        let timezone = TimeZone.current
        let seconds = -TimeInterval(timezone.secondsFromGMT(for: self))
        return Date(timeInterval: seconds, since: self)
    }
}

如果要本地日期和时间。试试这个代码：

NSString *localDate = [NSDateFormatter localizedStringFromDate:[NSDate date] dateStyle:NSDateFormatterMediumStyle timeStyle:NSDateFormatterMediumStyle];

将您的UTC日期转换为本地日期

-(NSString *)getLocalDateTimeFromUTC:(NSString *)strDate
{
    NSDateFormatter *dtFormat = [[NSDateFormatter alloc] init];
    [dtFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    [dtFormat setTimeZone:[NSTimeZone timeZoneWithAbbreviation:@"UTC"]];
    NSDate *aDate = [dtFormat dateFromString:strDate];

    [dtFormat setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    [dtFormat setTimeZone:[NSTimeZone systemTimeZone]];

    return [dtFormat stringFromDate:aDate];
}

像这样使用

NSString *localDate = [self getLocalDateTimeFromUTC:@"yourUTCDate"];

这里的输入是字符串currentUTCTime（格式为08/30/2012 11:11），将GMT中的输入时间转换为系统设置的区域时间

//UTC time
NSDateFormatter *utcDateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[utcDateFormatter setDateFormat:@"MM/dd/yyyy HH:mm"];
[utcDateFormatter setTimeZone :[NSTimeZone timeZoneForSecondsFromGMT: 0]];

// utc format
NSDate *dateInUTC = [utcDateFormatter dateFromString: currentUTCTime];

// offset second
NSInteger seconds = [[NSTimeZone systemTimeZone] secondsFromGMT];

// format it and send
NSDateFormatter *localDateFormatter = [[[NSDateFormatter alloc] init] autorelease];
[localDateFormatter setDateFormat:@"MM/dd/yyyy HH:mm"];
[localDateFormatter setTimeZone :[NSTimeZone timeZoneForSecondsFromGMT: seconds]];

// formatted string
NSString *localDate = [localDateFormatter stringFromDate: dateInUTC];
return localDate;

//This is basic way to get time of any GMT time.

NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
[formatter setDateFormat:@"hh:mm a"];  // 09:30 AM
[formatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:1]]; // For GMT+1
NSString *time = [formatter stringFromDate:[NSDate date]];  // Current time

使用适当的本地NSTimeZone将UTC日历中的日期转换为一个日期。

我写了这个方法将日期时间转换为我们的LocalTimeZone

-此处（NSString *）TimeZone参数是服务器时区

-(NSString *)convertTimeIntoLocal:(NSString *)defaultTime :(NSString *)TimeZone
{
    NSDateFormatter *serverFormatter = [[NSDateFormatter alloc] init];
    [serverFormatter setTimeZone:[NSTimeZone timeZoneWithAbbreviation:TimeZone]];
    [serverFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    NSDate *theDate = [serverFormatter dateFromString:defaultTime];
    NSDateFormatter *userFormatter = [[NSDateFormatter alloc] init];
    [userFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
    [userFormatter setTimeZone:[NSTimeZone localTimeZone]];
    NSString *dateConverted = [userFormatter stringFromDate:theDate];
    return dateConverted;
}

由于似乎没有人在使用NSDateComponents，所以我想我会投入...在此版本中，没有NSDateFormatter使用，因此没有字符串解析，NSDate也不用于表示GMT（UTC）以外的时间。原来NSDate在变量中i_date。

NSCalendar *anotherCalendar = [[NSCalendar alloc] initWithCalendarIdentifier:i_anotherCalendar];
anotherCalendar.timeZone = [NSTimeZone timeZoneWithName:i_anotherTimeZone];

NSDateComponents *anotherComponents = [anotherCalendar components:(NSCalendarUnitEra | NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond | NSCalendarUnitNanosecond) fromDate:i_date];

// The following is just for checking   
anotherComponents.calendar = anotherCalendar; // anotherComponents.date is nil without this
NSDate *anotherDate = anotherComponents.date;

i_anotherCalendar可以是NSCalendarIdentifierGregorian或任何其他日历。该NSString允许i_anotherTimeZone可以与被收购[NSTimeZone knownTimeZoneNames]，但anotherCalendar.timeZone可能是[NSTimeZone defaultTimeZone]或[NSTimeZone localTimeZone]或[NSTimeZone systemTimeZone]干脆。

它实际上anotherComponents是在新时区保存时间。您会发现anotherDate它等于i_date，因为它以格林尼治标准时间（UTC）表示时间。

您可以尝试以下一种方法：

NSDate *currentDate = [[NSDate alloc] init];
NSTimeZone *timeZone = [NSTimeZone defaultTimeZone];
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
[dateFormatter setDateStyle:NSDateFormatterLongStyle];
[dateFormatter setTimeStyle:NSDateFormatterLongStyle];
[dateFormatter setTimeZone:timeZone];
[dateFormatter setDateFormat:@"ZZZ"];
NSString *localDateString = [dateFormatter stringFromDate:currentDate];
NSMutableString *mu = [NSMutableString stringWithString:localDateString];
[mu insertString:@":" atIndex:3];
 NSString *strTimeZone = [NSString stringWithFormat:@"(GMT%@)%@",mu,timeZone.name];
 NSLog(@"%@",strTimeZone);

将UTC时间转换为当前时区。

通话功能

NSLocale *locale = [NSLocale autoupdatingCurrentLocale];

NSString *myLanguageCode = [locale objectForKey: NSLocaleLanguageCode];
NSString *myCountryCode = [locale objectForKey: NSLocaleCountryCode];

NSString *rfc3339DateTimeString = @"2015-02-15 00:00:00"];
NSDate *myDateTime = (NSDate*)[_myCommonFunctions _ConvertUTCTimeToLocalTimeWithFormat:rfc3339DateTimeString LanguageCode:myLanguageCode CountryCode:myCountryCode Formated:NO];

功能

-NSObject*)_ConvertUTCTimeToLocalTimeWithFormat:rfc3339DateTimeString     LanguageCode:(NSString *)lgc CountryCode:(NSString *)ctc Formated:(BOOL) formated
{
    NSDateFormatter *sUserVisibleDateFormatter = nil;
    NSDateFormatter *sRFC3339DateFormatter = nil;

    NSTimeZone *timeZone = [NSTimeZone defaultTimeZone];

    if (sRFC3339DateFormatter == nil)
    {
        sRFC3339DateFormatter = [[NSDateFormatter alloc] init];

        NSLocale *myPOSIXLocale = [[NSLocale alloc] initWithLocaleIdentifier:[NSString stringWithFormat:@"%@", timeZone]];

        [sRFC3339DateFormatter setLocale:myPOSIXLocale];
        [sRFC3339DateFormatter setDateFormat:@"yyyy'-'MM'-'dd'T'HH':'mm':'ss'Z'"];
        [sRFC3339DateFormatter setTimeZone:[NSTimeZone timeZoneForSecondsFromGMT:0]];
    }

    // Convert the RFC 3339 date time string to an NSDate.
    NSDate *date = [sRFC3339DateFormatter dateFromString:rfc3339DateTimeString];

    if (formated == YES)
    {
        NSString *userVisibleDateTimeString;

        if (date != nil)
        {
            if (sUserVisibleDateFormatter == nil)
            {
                sUserVisibleDateFormatter = [[NSDateFormatter alloc] init];
                [sUserVisibleDateFormatter setDateStyle:NSDateFormatterMediumStyle];
                [sUserVisibleDateFormatter setTimeStyle:NSDateFormatterShortStyle];
            }

            // Convert the date object to a user-visible date string.
            userVisibleDateTimeString = [sUserVisibleDateFormatter stringFromDate:date];

            return (NSObject*)userVisibleDateTimeString;
        }
    }

    return (NSObject*)date;
}