ios 时间转换

 double lastactivityInterval = [[singleFriendDict objectForKey:@"lastactivity"] doubleValue];

  NSDateFormatter* formatter = [[[NSDateFormatter alloc] init] autorelease];
  formatter.timeZone = [NSTimeZone timeZoneWithName:@"shanghai"];
  [formatter setDateStyle:NSDateFormatterMediumStyle];
  [formatter setTimeStyle:NSDateFormatterShortStyle];
  [formatter setDateFormat:@"MM月dd日 HH：mm"];


  NSDate* date = [NSDate dateWithTimeIntervalSince1970:lastactivityInterval];


  NSString* dateString = [formatter stringFromDate:date];

  lastActivityLabel.text = dateString;

  NSLog(@"format dateString:%@",dateString);