//是不是过了指定的天数- (BOOL) isAfterDays:(int) days {    NSDate * sendDate = [NSDate date];    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    NSString * locationString = [dateFormatter stringFromDate:sendDate];        NSString * lastShowTime = [[NSUserDefaults standardUserDefaults] objectForKey:@"lastShowTime"];    if (lastShowTime == nil) {        [[NSUserDefaults standardUserDefaults] setObject:locationString forKey:@"lastShowTime"];    }    else {        NSString * string = [self intervalSinceNow:lastShowTime];        int timeInterval = [string intValue];                NSLog(@"Interval:%@",string);        if (timeInterval >= days) {            [self saveLastShowTime];            return YES;        }    }        return NO;}//存储本次提醒时间，以便下次计算下次提醒的时间- (void) saveLastShowTime {    NSDate * sendDate = [NSDate date];    NSDateFormatter * dateFormatter = [[NSDateFormatter alloc] init];    [dateFormatter setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    NSString * locationString = [dateFormatter stringFromDate:sendDate];    [[NSUserDefaults standardUserDefaults] setObject:locationString forKey:@"lastShowTime"];}#pragma mark 获取指定日期距离现在的时间段- (NSString *)intervalSinceNow: (NSString *) theDate{        NSDateFormatter *date=[[NSDateFormatter alloc] init];    [date setDateFormat:@"yyyy-MM-dd HH:mm:ss"];    NSDate *d=[date dateFromString:theDate];        NSTimeInterval late=[d timeIntervalSince1970]*1;            NSDate* dat = [NSDate dateWithTimeIntervalSinceNow:0];    NSTimeInterval now=[dat timeIntervalSince1970]*1;    NSString *timeString=@"";        NSTimeInterval cha=now-late;        //**********    timeString = [NSString stringWithFormat:@"%f", cha/86400];    timeString = [timeString substringToIndex:timeString.length-7];    timeString=[NSString stringWithFormat:@"%@", timeString];    //*********        return timeString;}