Solution for Astro Baltics on-site test-assignment that must be solved in 1-2 hours.

calculator.php

<?php

function calculateWorkingHours(string $workStartTime, string $workEndTime, string $dayStartTime = '06:00', string $dayEndTime = '22:00'): array
{
    $dateTime = DateTime::createFromFormat('H:i', $workStartTime);
    $timeCursor = $dateTime->format('H:i');
    $interval = new DateInterval('PT15M');
    $dayUnits = $nightUnits = 0;

    do {
        $nextInterval = $dateTime->add($interval);
        $timeCursor = $nextInterval->format('H:i');

        if ($dayStartTime < $timeCursor && $dayEndTime >= $timeCursor) {
            $dayUnits++;
        } else {
            $nightUnits++;
        }
    } while ($workEndTime != $timeCursor);

    return [
        'day' => $dayUnits / 4,
        'night' => $nightUnits / 4
    ];
}

Write a function that calculates night shift (22:00 - 06:00) hours and dayshift hours (06:00 - 22:00) between given range of time. Function takes 2 parameters that represent work starting time and end time. Input parameters are 15-minutes precision (quarter of an hour) and do not need to be validated, you can safely assume that they are correct. Your function must respect the quarter of an hour precision in calculations as well.

For example function("20:15", "03:00") would return 1.75h day shift and 5h night shift.