timezone_string-absurdity.php

<?php
/**
 * Attempts to retrieve the WP timezone, or if not set, the timezone derived from the gmt_offset.
 *
 * @access private
 * @since  2.2
 *
 * @return string Timezone string, or if all checks fail, default is 'UTC'.
 */
private function get_core_timezone() {

	// Passing a $default value doesn't work for the timezeon_string option.
	$timezone = get_option( 'timezone_string' );

	/*
	 * If the timezone isn't set, or rather was set to a UTC offset, core saves the value
	 * to the gmt_offset option and leaves timezone_string empty – because that makes
	 * total sense, obviously. ¯\_(ツ)_/¯
	 *
	 * So, try to use the gmt_offset to derive a timezone.
	 */
	if ( empty( $timezone ) ) {
		// Try to grab the offset instead.
		$gmt_offset = get_option( 'gmt_offset', 0 );

		// Yes, core returns it as a string, so as not to confuse it with falsey.
		if ( '0' !== $gmt_offset ) {
			$timezone = timezone_name_from_abbr( '', (int) $gmt_offset * HOUR_IN_SECONDS, date( 'I' ) );
		}

		// If the offset was 0 or $timezone is still empty, just use 'UTC'.
		if ( '0' === $gmt_offset || empty( $timezone ) ) {
			$timezone = 'UTC';
		}
	}

	return $timezone;
}