iOS开发NSDate、NSString、时间戳之间的转化

//将UTCDate(世界标准时间)转化为当地时区的标准Date（钟表显示的时间）

//NSDate *date = [NSDate date];   2018-03-27 06:54:41 +0000 
//转化后：2018-03-27 14:54:41 +0000 
-(NSDate *)getLocalDateFromUTCDate:(NSDate *)UTCDate{
  NSTimeZone *tz = [NSTimeZone defaultTimeZone]; 
 NSInteger seconds = [tz secondsFromGMTForDate: UTCDate];  
 return [NSDate dateWithTimeInterval: seconds sinceDate: UTCDate];
 }

//将当地时区的标准Date转化为UTCDate 
//当前当地的标准时间：2018-03-27 14:54:41 +0000 
//转化为世界标准时间:2018-03-27 06:54:41 +0000 
-(NSDate *)getUTCDateFromLocalDate:(NSDate *)LocalDate{
 NSTimeZone *tz = [NSTimeZone defaultTimeZone];
 NSInteger seconds = -[tz secondsFromGMTForDate: LocalDate];
 return [NSDate dateWithTimeInterval: seconds sinceDate: LocalDate];
 }

//根据UTCDate获取当前时间字符串（钟表上显示的时间）
 //输入：[NSDate date]     2018-03-27 07:44:05 +0000
 //输出：2018-03-27 15:44:05  
-(NSString *)localStringFromUTCDate:(NSDate *)UTCDate{
 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc]init]; 
NSTimeZone *tz = [NSTimeZone defaultTimeZone];  
[dateFormatter setTimeZone:tz];
 [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSString* result=[dateFormatter stringFromDate:UTCDate]; 
return result; 
}

//根据UTC字符串获取当前时间字符串（钟表上显示的时间）
 //输入：2018-03-27 07:44:05
 //输出：2018-03-27 15:44:05
 -(NSString *)localStringFromUTCString:(NSString *)UTCString{ 
//先将UTC字符串转为UTCDate; 
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *tz = [NSTimeZone timeZoneWithAbbreviation:@"GMT"];
 [dateFormatter setTimeZone:tz]; 
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *UTCDate = [dateFormatter dateFromString:UTCString];  
[dateFormatter setTimeZone:[NSTimeZone defaultTimeZone]];
NSString* result = [dateFormatter stringFromDate:UTCDate];  
return result;  }

//将当前时间字符串转为UTCDate 
-(NSDate *)UTCDateFromLocalString:(NSString *)localString{
 NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init]; 
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *date = [dateFormatter dateFromString:localString]; 
return date;
}

//将当前时间字符串转为UTC字符串 
 -(NSString *)UTCStringFromLocalString:(NSString *)localString{
NSDate *date = [self UTCDateFromLocalString:localString]; 
NSString *string= [NSString stringWithFormat:@"%@",date]; 
NSString *result = [stringsubstringToIndex:string.length-6]; 
return result;  
}

//UTCDate转UTC字符串
-(NSString *)UTCStringFromUTCDate:(NSDate *)UTCDate{ 
NSDateFormatter *dataFormatter = [[NSDateFormatter alloc]init]; 
[dataFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSTimeZone *tz = [NSTimeZone timeZoneWithAbbreviation:@"GMT"]; 
[dataFormatter setTimeZone:tz];
NSString *UTCString = [dataFormatter stringFromDate:UTCDate]; 
return UTCString;
 }

//将当前时间（UTCDate）转为时间戳
 -(NSString *)timeStampFromUTCDate:(NSDate *)UTCDate{
 NSTimeInterval timeInterval = [UTCDate timeIntervalSince1970]; 
// *1000,是精确到毫秒；这里是精确到秒; 
NSString *result = [NSString stringWithFormat:@"%.0f",timeInterval];
return result; 
}

//当前时间字符串(钟表上显示的时间)转为时间戳 
-(NSString *)timeStamapFromLocalString:(NSString *)localString{
//先转为UTCDate 
NSDate *UTCDate = [self UTCDateFromLocalString:localString];
NSString *timeStamap = [self timeStampFromUTCDate:UTCDate];
return timeStamap;
}

//将UTCString转为时间戳
-(NSString *)timeStamapFromUTCString:(NSString *)UTCString{
//先将UTC字符串转为UTCDate;
NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
NSTimeZone *tz = [NSTimeZone timeZoneWithAbbreviation:@"GMT"]; 
[dateFormatter setTimeZone:tz];
[dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];
NSDate *UTCDate = [dateFormatter dateFromString:UTCString];
NSString *timeStamap = [self timeStampFromUTCDate:UTCDate];
return timeStamap;
}

//时间戳转UTCDate
-(NSDate *)UTCDateFromTimeStamap:(NSString *)timeStamap{
NSTimeInterval timeInterval=[timeStamap doubleValue];
//   1000; 传入的时间戳timeStamap如果是精确到毫秒的记得要/1000
NSDate *UTCDate=[NSDate dateWithTimeIntervalSince1970:timeInterval];
return UTCDate;
}