Echo durations from multiple dates (ex. Aug 25-27, Sep 3)

Question

I'm dealing with events that can either take place on a single day (ex. 5/20) or multiple days (ex. 8/25, 8/26, 8/27, 9/3).

Given, for example, a 4-day event taking place on 8/25, 8/26, 8/27, and 9/3, I'd like to echo this:

Aug 25-27, Sep 3

I'd like the code to:

• Handle single day events (ex. Oct 3)
• Group consecutive days (ex. Jan 25-27)
• Separate non-consecutive days with a comma (ex. Sep 19, 22)
• Handle a range of dates spanning multiple months (ex. Feb 28-Mar 2)
• Handle multiple ranges if necessary (ex. Apr 2-4, Jun 10-13)
• Avoid redundant date info (ex. Dec 1-3, Dec 8)

This is easy to do with only a single-day event using date() formatting, but is it possible to intelligently produce formatting like this using multiple dates when necessary?

Answer 1

I made a function that should output the required string based on an array of DateTime objects. I placed some inline comments to indicate what is happening at a given time in the function.

function produceDateString(array $dates): string
{
    // sort the dates
    sort($dates);

    // create an array of arrays that contain ranges of consecutive days
    $ranges = [];
    $currentRange = [];
    foreach ($dates as $date) {
        if(empty($currentRange) || consecutive(end($currentRange), $date)) {
            $currentRange[] = $date;
        } else {
            $ranges[] = $currentRange;
            $currentRange = [$date];
        }
    }
    $ranges[] = $currentRange;

    // create the output string
    $output = '';
    $previous = null;
    foreach ($ranges as $range) {
        // add a comma between each range
        if (!empty($output)) {
            $output .= ', ';
        }

        // the long format should be used on the first occurrence of the loop
        // or when the month of first date in the range doesn't match 
        // the month of the last date in the previous range
        $format = $previous === null || end($previous)->format('m') !== reset($range)->format('m')
            ? 'M. j'
            : 'j';

        // the output differes when there are 1 or multiple dates in a range
        if (count($range) > 1) {
            // the output differs when the end and start are in the sane month
            $output .= sameMonth(reset($range), end($range))
                ? reset($range)->format($format).'-'.end($range)->format('j')
                : reset($range)->format('M. j').'-'.end($range)->format('M. j');
        } else {
            $output .= reset($range)->format($format);
        }

        $previous = $range;
    }

    return $output;
}

function consecutive(DateTime $t1, DateTime $t2): bool
{
    $t1->setTime(0, 0, 0, 0);
    $t2->setTime(0, 0, 0, 0);
    return(abs($t2->getTimestamp() - $t1->getTimestamp()) < 87000);
}

function sameMonth(DateTime $t1, DateTime $t2): bool
{
    return $t1->format('Y-m') === $t2->format('Y-m');
}

I made a small 3v4l to show you how it works exactly. Don't hesitate to ask if you might have any questions about how this works.