时间差计算

 

//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;

}