filter dates in php in accordance with timezone selected from UI

I am working on a php code as shown below which has air_date which I want to be changed when different timezone is selected from UI.

Php code:

$cols = array(
    'e.description_' . $opp_lang . ' as translation',
    's.air_date',  // This is the entry point of air_date and its been used everywhere. 
    'e.program_id',
); 

Logic I have used for timezone:

function tz_translations( $lang = 'en' ) {
    $tz_translations = [
        'en' => [
            'PST' => [
                'label' => 'PT',
                'diff'  => 'subtract 3 hours',
            ],
            'EST' => [
                'label' => 'ET',
                'diff'  => 'subtract 0 hours',
            ],
        ],
        'fr' => [
            'HNP' => [
                'label' => 'HP',
                'diff'  => 'subtract 3 hours',
            ],
            'HNE' => [
                'label' => 'HE',
                'diff'  => 'subtract 0 hours',
            ],
        ],
    ];

    return $tz_translations[ $lang ];
}   

UI (JS Code):

<ul id="js-timezone-picker">
   <?php foreach ( $tz_translations as $key => $tz ) :
      $tz_param = strtolower( $tz['label'] );
      $active = ( $current_tz === $key ) ? 'active' : '';
      ?>
   <li>
      <button id="<?php echo esc_attr( 'js-time-' . $tz_param ) ?>"
         class="<?php echo sanitize_html_class( $active ) ?>"
         data-timezone="<?php echo esc_attr( $tz_param ) ?>"><?php echo esc_html( $tz['label'] ) ?></button>
   </li>
   <?php endforeach; ?>
</ul>

When PT/ET is selected then it becomes the following on inspect:

<button id="js-time-pt" class="" data-timezone="pt">PT</button>
<button id="js-time-et" class="" data-timezone="et">ET</button>

Problem Statement:

I am wondering what changes I should make in the php code above so that when different time-zones is selected from the UI/JS code, air_date in the php code gets changed automatically in accordance with time-zones.

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