iOS时间处理

// 剩余时间处理
    // 当前时间 2014-08-27 09:06
    NSDate *now = [NSDate date];
    // 过期时间 2014-08-28 00:00
    NSDateFormatter *fmt = [[NSDateFormatter alloc] init];
    fmt.dateFormat = @"yyyy-MM-dd";
    NSDate *deadTime = [[fmt dateFromString:self.deal.purchase_deadline] dateByAddingTimeInterval:24 * 3600];
    // 比较2个时间的差距
    NSCalendar *calendar = [NSCalendar currentCalendar];
    NSCalendarUnit unit = NSCalendarUnitDay | NSCalendarUnitHour | NSCalendarUnitMinute;
    NSDateComponents *cmps = [calendar components:unit fromDate:now toDate:deadTime options:0];
    if (cmps.day > 365) {
        self.leftTimeButton.title = @"一年内不过期";
    } else {
        self.leftTimeButton.title = [NSString stringWithFormat:@"%d天%d小时%d分", cmps.day, cmps.hour, cmps.minute];
    }