Why is this time difference when I use "IntlDateFormatter"? - php

Question

Why is this time difference when I use "IntlDateFormatter"?
<?php
// php v7.1
$pattern = 'yyyy-MM-dd HH:mm:ss';
$timezone = "Europe/Budapest";
$inputDateTimeStr = '1890-01-01 00:00:00';
$locale = 'hu_HU';
$intlDateFormatter = new \IntlDateFormatter( $locale, \IntlDateFormatter::MEDIUM, \IntlDateFormatter::SHORT, \IntlTimeZone::createTimeZone($timezone), \IntlDateFormatter::GREGORIAN, $pattern
);
$dateTime = new \DateTime($inputDateTimeStr);
$dateTime->setTimezone(new \DateTimeZone($timezone));
$outputDateTimeStr = $intlDateFormatter->format($dateTime->getTimestamp());
print ' in: ' . $inputDateTimeStr
. ' out: ' . $outputDateTimeStr // string(19) "1890-01-01 00:16:20"
. ' diff: ' . ( strtotime($outputDateTimeStr) - strtotime($inputDateTimeStr) ) . ' seconds';
Output: in: 1890-01-01 00:00:00 out: 1890-01-01 00:16:20 diff: 980 seconds

Answer 1

I think, the intlDateFormatter and DateTime are before 1890 not compatible.
The Middle European Time (MET) was introduced step for step in Europe after 1890.
At the beginning of 1890 each place had its own time, depending on its longitude.
The following code shows this for 4 examples.
$refDate = date_create('1890-01-01 UTC');
$ts = $refDate->getTimeStamp();
$pattern = 'yyyy-MM-dd HH:mm:ss';
$timezones = [
"Europe/Paris", //2.3522° E
"Europe/Berlin", //13.4050° E
"Europe/Prague", //14.4378° E
"Europe/Budapest"//19.0402° E
];
$locale = 'hu_HU';
foreach($timezones as $timezone){
$intlDateFormatter = new \IntlDateFormatter(
$locale,
\IntlDateFormatter::MEDIUM,
\IntlDateFormatter::SHORT,
\IntlTimeZone::createTimeZone($timezone),
\IntlDateFormatter::GREGORIAN,
$pattern
);
$outputDateTimeStr = $intlDateFormatter->format($ts);
echo $timezone.": ".$outputDateTimeStr."<br>";
}
Output
Europe/Paris: 1890-01-01 00:09:21
Europe/Berlin: 1890-01-01 00:53:28
Europe/Prague: 1890-01-01 00:57:44
Europe/Budapest: 1890-01-01 01:16:20
DateTime delivers other results.