success

<?php
$input=file_get_contents ('C:\wamp64\www\naplo.txt','r')  or
exit('Unable to open the file!');

$fulldiary=new DiaryParser();

class DiaryRecord
{

    /**
     * @var \DateTime
     */
    public $date;

    /**
     * @var string
     */
    public $name = '';

    /**
     * @var string[]
     */
    public $attendance = [];

}
class DiaryParser
{
    /**
     * @var int
     */
    protected $year = 2017;

    protected $time='12:00';

    /**
     * @return \DiaryRecord[]
     */
    public function parse(string $diary): array
    {
        $records = [];
        $days = explode('# ', trim($diary, "# \t\r\n"));
        $days = array_filter($days);
        foreach ($days as $day) {
            $lines = $this->splitLines($day);
            $date = $this->parseDateLine(array_shift($lines));
            foreach ($lines as $absenceLine) {
                $absenceLine = $this->parseAbsenceLine($absenceLine);

                $record = new DiaryRecord();
                $record->date = $date;
                $record->name = $absenceLine['name'];
                $record->attendance = $absenceLine['attendance'];

                $records[] = $record;
            }
        }

        return $records;
    }
    protected function splitLines(string $text): array
    {
        return explode("\n",trim($text,"\n"));
    }
    protected function parseDateLine(string $line): string
    {
        $d=explode(" ",trim($line));
        return strval($this->year).'-'.$d[0].'-'.$d[1].' '.($this->time);
    }
    protected function parseAbsenceLine(string $line): array
    {
    return [
        'name' => mb_substr($line,0,-8),
        'attendance' => preg_split('//', mb_substr($line, -7), -1, PREG_SPLIT_NO_EMPTY)
    ];
    }

}
print_r ($fulldiary->parse($input));