包含许多列的HTML表格需要很长时间才能呈现

Question

I'm trying to make a "map" of holidays and for that I need every month with every day they have in the header and the names of each employee at the left columns, till there I have no problems, the problem is the browser is taking too long to load and after load it breaks my navigation with hashtags ( can't load another view in the "content" section ).

Building the header:

$year_start = new DateTime('1-1-2016');
$year_end = new DateTime('1-5-2017');
$period = new DatePeriod($year_start, new DateInterval('P1D'), $year_end);
$period_m = new DatePeriod($year_start, new DateInterval('P1M'), $year_end);

<thead>
    <?php
    echo '<tr>';
    echo '<th colspan="2"></th>';
    foreach ($period_m as $month){  
        echo '<th style="text-align:center;" colspan="'.cal_days_in_month(CAL_GREGORIAN, $month->format('m'), $month->format('Y')).'">'.$month->format('F').'</th>';
    }
    echo "</tr>";
    echo "<tr>";
    ?>
    <th> Name</th>
    <th> Department</th>
    <?php
    foreach($period as $day){
        echo "<th>" . $day->format('j')."</th>";
    }
    echo "</tr>";
    ?>
</thead>`

Building the body ( that's what takes to long )

<tbody >
        <tr>
            <td><?=$user['name']?></td>
            <td><?=$user['department']?></td>
        <?php
        foreach($period as $day){
            if ($day->format('N') === '7' || $day->format('N') === '6') {
                echo '<td class="weekend"></td>'; 
            }else if(in_array($day->format('Y-n-j'), $holidayDays) || in_array($day->format('*-n-j'), $holidayDays)){
                echo '<td class="holiday"></td>'; 
            }else{
                if(isset($user['dates']) && in_array($day->format('Y-n-j'),$user['dates'])){
                    echo '<td class="user-holiday"> 1 </td>'; 
                }else{
                    echo '<td></td>';   
                }
            }
        }
        ?>
        </tr>
    <?php       
    }
    ?>
    </tbody>

With Firefox developer I tried to analyse the speed and the slowest are those ones:

Recalcute Style duration = 5 905,15 ms

Layout duration = 3 289,58 ms

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