Source

File: wp-includes/formatting.php

function iso8601_to_datetime( $date_string, $timezone = 'user' ) {
	$timezone    = strtolower( $timezone );
	$wp_timezone = wp_timezone();
	$datetime    = date_create( $date_string, $wp_timezone ); // Timezone is ignored if input has one.

	if ( false === $datetime ) {
		return false;
	}

	if ( 'gmt' === $timezone ) {
		return $datetime->setTimezone( new DateTimeZone( 'UTC' ) )->format( 'Y-m-d H:i:s' );
	}

	if ( 'user' === $timezone ) {
		return $datetime->setTimezone( $wp_timezone )->format( 'Y-m-d H:i:s' );
	}

	return false;
}