IOS 时间和时间戳之间转化示例

- (NSString *)timeWithTimeIntervalString:(NSString *)timeString{  // 格式化时间  NSDateFormatter* formatter = [[NSDateFormatter alloc] init];  formatter.timeZone = [NSTimeZone timeZoneWithName:@"shanghai"];  [formatter setDateStyle:NSDateFormatterMediumStyle];  [formatter setTimeStyle:NSDateFormatterShortStyle];  [formatter setDateFormat:@"yyyy年MM月dd日 HH:mm"];    // 毫秒值转化为秒  NSDate* date = [NSDate dateWithTimeIntervalSince1970:[timeString doubleValue]/ 1000.0];  NSString* dateString = [formatter stringFromDate:date];  return dateString;}

    // 当前时间   NSDate* date = [NSDate dateWithTimeIntervalSinceNow:0];  NSTimeInterval a=[date timeIntervalSince1970]*1000; // *1000 是精确到毫秒，不乘就是精确到秒  NSString *timeString = [NSString stringWithFormat:@"%.0f", a]; //转为字符型

- (void)getBabyDetailAge:(NSString *)date{  // 获得日期对象  NSDateFormatter *formatter_ = [[NSDateFormatter alloc] init];  formatter_.dateFormat = @"yyyy-MM-dd HH:mm:ss";  NSDate *createDate = [formatter_ dateFromString:date];    NSCalendar *gregorian = [[ NSCalendar alloc ] initWithCalendarIdentifier : NSCalendarIdentifierGregorian];  NSUInteger unitFlags = NSCalendarUnitDay | NSCalendarUnitMonth | NSCalendarUnitYear;  NSDateComponents *components = [gregorian components:unitFlags fromDate:createDate toDate:[NSDate date] options: 0 ];    NSInteger years = [components year];  NSInteger months = [components month ];  NSInteger days = [components day ];}