Add the date and time range to a url param from the Calendar. The filter hook isn't present within the tooltip, so this only adds to the calendar item.

my_custom_calendar_url_params.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

add_filter(
    'FHEE__EE_Datetime_In_Calendar__to_array_for_json__url',
    'my_custom_calendar_url_params', 
    10, 
    3
);
function my_custom_calendar_url_params($url, $event, $obj) {
    $value = '';
    $datetime = $obj->datetime();
    if($datetime instanceOf EE_Datetime) {
        $value .= $datetime->date_and_time_range('Y_m_d', 'H_i', '-', '_');
        $url = add_query_arg('datetime', $value, $event->get_permalink());
    }
    return $url;
};

my_inline_script_ts_from_cal_param.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file
// This is an example that shows how to use the datetime parameter from the calendar to style a specific ticket related to a specific datetime

add_action('wp_enqueue_scripts', 'my_add_inline_script_ts_from_cal_param', 20);
function my_add_inline_script_ts_from_cal_param() {
    $custom_js = '
    jQuery(document).ready(function($){
            var urlParams = new URLSearchParams(window.location.search);
    if(urlParams.has("datetime")){
        var dParam = urlParams.get("datetime");
        var styles = {
            "background-color" : "#d1d1f9",
            "transition" : "background-color 5000ms"
        };
        $(".ee-ticket-datetimes-" + dParam).css( styles );
    }         
    });';
    wp_add_inline_script('ticket_selector', $custom_js);
}