laybuy-gateway-for-woocommerce/includes/wc-functions.php

<?php
if( !function_exists('wp_get_timezone_string') ) {
    /**
     * Returns the timezone string for a site, even if it's set to a UTC offset
     *
     * Adapted from http://www.php.net/manual/en/function.timezone-name-from-abbr.php#89155
     *
     * @return string valid PHP timezone string
     */
    function wp_get_timezone_string() {

        // if site timezone string exists, return it
        if ( $timezone = get_option( 'timezone_string' ) )
            return $timezone;

        // get UTC offset, if it isn't set then return UTC
        if ( 0 === ( $utc_offset = get_option( 'gmt_offset', 0 ) ) )
            return 'UTC';

        // adjust UTC offset from hours to seconds
        $utc_offset *= 3600;

        // attempt to guess the timezone string from the UTC offset
        if ( $timezone = timezone_name_from_abbr( '', $utc_offset, 0 ) ) {
            return $timezone;
        }

        // last try, guess timezone string manually
        $is_dst = date( 'I' );

        foreach ( timezone_abbreviations_list() as $abbr ) {
            foreach ( $abbr as $city ) {
                if ( $city['dst'] == $is_dst && $city['offset'] == $utc_offset )
                    return $city['timezone_id'];
            }
        }

        // fallback to UTC
        return 'UTC';
    }
}