NSString *timeStr = @"2019-06-28 12:12:12";
// 1.将时间转换为date
NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
formatter.dateFormat = @"yyyy-MM-dd HH:mm:ss";
NSDate *date1=[NSDate date];
NSDate *date2 = [formatter dateFromString:timeStr];
// 2.创建日历
NSCalendar *calendar = [NSCalendar currentCalendar];
NSCalendarUnit type = NSCalendarUnitYear | NSCalendarUnitMonth | NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute | NSCalendarUnitSecond;
// 3.利用日历对象比较两个时间的差值
NSDateComponents *cmps = [calendar components:type fromDate:date1 toDate:date2 options:0];
// 4.输出结果
NSLog(@"时间差%ld年%ld月%ld日%ld小时%ld分钟%ld秒", cmps.year, cmps.month, cmps.day, cmps.hour, cmps.minute, cmps.second);
