AS2: Calculate days between two dates

问题:

I use this script currently to determine the difference between two dates:

// Slide_Tracker[?].date_int are results from the built in function getTime()
var current_date = new Date(Slide_Tracker[i].date_int);
var past_date:Date = new Date(Slide_Tracker[i - 1].date_int);
var date_diff:Number = Math.round((current_date - past_date) / 86400000);

The problem with this is I want to monitor the actual physical day change so if someone accessed the application at 11:59 PM and then came back 5 minutes later this would register as a 1 day difference (a new day), this current script requires atleast 12 hours to have passed between two dates for it to register as a new day.

I have thought about using the date number etc, but because months and years are so different it is quite a complex route, there must be something simpler.

回答1:

As an FYI, the difference between a date and midnight of the following AM is:

// dt is the start date
var diff:Number = 
      new Date(dt.getYear(), dt.getMonth(), dt.getDate() + 1) - dt.getTime()

But it is easiest to simply round to the next day and then start from there:

var dt:Date = new Date(Slide_Tracker[i - 1].date_int);
var past_date = // start at the next day to only deal w/ 24 hour increments
    new Date(dt.getYear(), dt.getMonth(), dt.getDate() + 1);
dt = new Date(Slide_Tracker[i].date_int);
var current_date = 
    new Date(dt.getYear(), dt.getMonth(), dt.getDate() + 1);
var date_diff:Number = Math.round((current_date.getTime() - 
                                   past_date.getTime()) / 86400000);

Your other option is to round the inputs:

// rounds a timestamp *down* to the current day
function getBaseDay(val:Number):Number
{
    return Math.floor( val / 86400000 ) * 86400000
}

var current_date = new Date(getBaseDay(Slide_Tracker[i].date_int));
var past_date:Date = new Date(getBaseDay(Slide_Tracker[i - 1].date_int));
var date_diff:Number = Math.round((current_date.getTime() - 
                                   past_date.getTime()) / 86400000);

回答2:

Something like this should work:

public boolean isNewDay( current:Date, past:Date ):Boolean
{
    // check the days of the month first
    if( current.date != past.date )
        return true;

    // check the months in case they came back on the same day of the next month
    if( current.month != past.month )
        return true;

    // finally check the year, in case they came back on the same day the next year
    if( current.fullYear != past.fullYear )
        return true;

    return false;
}

even though you've accepted the answer, here's an update function:

public function getNumberOfDays( current:Date, past:Date ):int
{
    // get the number of millis between the two dates
    var millis:Number = current.time - past.time;

    // a day in millis is 1000 (s) * 60 (m) * 60 (h) * 24 (day)
    var day:Number = 1000 * 60 * 60 * 24;

    // get the number of days
    var numDays:int = int( millis / day );

    // create midnight of the current day
    if ( numDays == 0 )
    {
        // if our numDays is 0, check if the current date is after midnight and the
        // previous date was before midnight the previous day, in which case, count
        // it as another day
        var midnight:Date = new Date( current.fullYear, current.month, current.date );
        if ( current.time > midnight.time && past.time < midnight.time )
            numDays++;
    }

    return numDays;
}

It works with all the test cases I've tried (midnight to 23.59.59 = 0 days, 23.59 to 00.05 = 1 day)