objective-c - 计算两个日期之间的白天时间和夜间时间

Question

我正在尝试以秒为单位计算两个日期之间的白天时间和夜间时间，假设“夜间时间”定义为晚上 8:00 到上午 7:59，“白天时间”定义为 8:上午 00 点至晚上 7:59。我将与当前时间戳进行比较的过去日期始终比现在时间短 24 小时。

我该怎么做？

Answer 1

当您开始处理夏令时等问题时，这很快就会变得复杂，因此您确实需要使用当前日历并使用日历/日期函数来计算时差。

例如，如果时钟在凌晨 3:00 向前拨动 1 小时，则根据您的定义，在时间更改当天您应该有 11 个小时的“夜晚”(而不是 12 个小时)。

我还没有彻底测试这段代码，但它应该非常接近:

// 8:00:00 AM in seconds
static const NSTimeInterval daytimeStart = 28800;
// 8:00:00 PM in seconds
static const NSTimeInterval daytimeStop  = 72000;

// Convert date to a "time" which is the number of seconds since midnight, NOT considering time changes
- (NSTimeInterval)getTimeForDate:(NSDate *)date {
    NSCalendar *cal = [NSCalendar currentCalendar];

    NSDateComponents *dateComps = [cal components:NSHourCalendarUnit | 
                                                    NSMinuteCalendarUnit | 
                                                    NSSecondCalendarUnit
                                         fromDate:date];
    NSTimeInterval time = dateComps.hour * 3600 + dateComps.minute * 60 + dateComps.second;
    return time;
}

// Set the time to the specified hour and minutes/seconds to 0
- (NSDate *)dateBySettingTimeToBeginningOfHour:(NSUInteger)hour ofDate:(NSDate *)date {
    NSCalendar *cal = [NSCalendar currentCalendar];

    NSDateComponents *dateComps = [cal components:NSYearCalendarUnit |
                                   NSMonthCalendarUnit |
                                   NSDayCalendarUnit |
                                   NSHourCalendarUnit | 
                                   NSMinuteCalendarUnit | 
                                   NSSecondCalendarUnit
                                         fromDate:date];
    [dateComps setHour:hour];
    [dateComps setMinute:0];
    [dateComps setSecond:0];
    NSDate *newDate = [cal dateFromComponents:dateComps];
    return newDate;
}

// Add one day to the current date
- (NSDate *)dateByAddingOneDayToDate:(NSDate *)date {
    NSCalendar *cal = [NSCalendar currentCalendar];

    NSDateComponents *dateComps = [cal components:NSYearCalendarUnit |
                                   NSMonthCalendarUnit |
                                   NSDayCalendarUnit |
                                   NSHourCalendarUnit | 
                                   NSMinuteCalendarUnit | 
                                   NSSecondCalendarUnit
                                         fromDate:date];
    [dateComps setDay:[dateComps day] + 1];
    NSDate *newDate = [cal dateFromComponents:dateComps];
    return newDate;
}

// Check to see if it is daytime
- (BOOL)isDayForDate:(NSDate *)date {
    NSTimeInterval time = [self getTimeForDate:date];
    if (time >= daytimeStart) {
        if (time < daytimeStop) {
            return YES;
        }
    }

    // Default
    return NO;
}

// Check to see if it is night
- (BOOL)isNightForDate:(NSDate *)date {
    return ![self isDayForDate:date];
}

// When do we transition from day to night or night to day next?
- (NSDate *)dateForNextTransitionForDate:(NSDate *)date {
    NSTimeInterval time = [self getTimeForDate:date];
    if (time < daytimeStart) {
        return [self dateBySettingTimeToBeginningOfHour:8 ofDate:date];
    }

    if (time < daytimeStop) {
        return [self dateBySettingTimeToBeginningOfHour:20 ofDate:date];
    }

    // Tomorrow morning
    NSDate *newDate = [self dateByAddingOneDayToDate:date];
    newDate = [self dateBySettingTimeToBeginningOfHour:8 ofDate:newDate];
    return newDate;
}

- (NSTimeInterval)nightTimeFromDate:(NSDate *)startingDate toDate:(NSDate *)laterDate {
    if ([startingDate compare:laterDate] != NSOrderedAscending) {
        return 0;
    }

    NSTimeInterval nightTime    = 0;
    NSDate *now                 = laterDate;
    NSDate *transitionDate      = startingDate;
    NSDate *loopDate            = startingDate;
    BOOL isNight                = [self isNightForDate:startingDate];

    do {
        transitionDate = [self dateForNextTransitionForDate:transitionDate];
        if ([transitionDate compare:now] == NSOrderedDescending) {
            transitionDate = now;
        }

        if (isNight) {
            nightTime = nightTime + [transitionDate timeIntervalSinceDate:loopDate];
        }

        loopDate = transitionDate;
        isNight = !isNight;
    } while ([transitionDate compare:now] != NSOrderedSame);

    return nightTime;
}

- (NSTimeInterval)dayTimeFromDate:(NSDate *)startingDate toDate:(NSDate *)laterDate {
    if ([startingDate compare:laterDate] != NSOrderedAscending) {
        return 0;
    }

    NSTimeInterval diff = [laterDate timeIntervalSinceDate:startingDate];
    diff = diff - [self nightTimeFromDate:startingDate toDate:laterDate];
    return diff;
}

// Example usage:
NSDate *now  = [NSDate date];
NSDate *date = [NSDate dateWithTimeInterval:-82800 sinceDate:now];

NSLog(@"%f", [self nightTimeFromDate:date toDate:now]);
NSLog(@"%f", [self dayTimeFromDate:date toDate:now]);

// Results are 43200.000000 and 39600.000000 right now in the middle of the day.