Previous code
[code type="markup"]
<thead>
<tr>
    <th>#</th>
    <th>Session</th>
    <th>Speaker(s)</th>
    <th>Time</th>
    <th>Venue</th>
</tr>
</thead>
[/code]
New code
[code type="markup"]
<thead>
<tr>
    <th>#</th>
    <th><?php echo JText::_('COM_SPEVENTUM_SESSION'); ?></th>
    <th><?php echo JText::_('COM_SPEVENTUM_SPEAKERS'); ?></th>
    <th><?php echo JText::_('COM_SPEVENTUM_TIME'); ?></th>
    <th><?php echo JText::_('COM_SPEVENTUM_VENUE'); ?></th>
</tr>
</thead>
[/code]

Added this language code inside the en-GB.tpl_shaper_eventum.ini file
[code type="markup"]
COM_SPEVENTUM_SESSION="Sesja"
COM_SPEVENTUM_SPEAKERS="Głośniki"
COM_SPEVENTUM_TIME="Godziny"
COM_SPEVENTUM_VENUE="Miejsce"
[/code]

-Thanks