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Bug #71945 Wrong timecalc prior 1956 -> summertime?
Submitted: 2016-04-01 15:49 UTC Modified: 2016-04-04 14:02 UTC
From: snoopyf at gmx dot net Assigned:
Status: Not a bug Package: Date/time related
PHP Version: Irrelevant OS: Linux
Private report: No CVE-ID: None
View Developer Edit
 [2016-04-01 15:49 UTC] snoopyf at gmx dot net 
Description:
------------
Having this Unix Timestamp:
-433044000

and date.timezone in php.ini is set to "Europe/Berlin" this function:
date("Y-m-d H:i:s");

returns:
1956-04-11 23:00:00

Test script:
---------------
<?php
echo(date_default_timezone_get());
echo(date("Y-m-d H:i:s",-433044000));
?>


Expected result:
----------------
The result should be:

1956-04-12 00:00:00

For me this seems to be summertime - related as 1956 was the current beginnig of summertime changes...

Checking with JavaScript on the same machine gives the correct result:

<script language="JavaScript">
        var d=new Date(-433044000*1000); // *1000 as JavaScripts Date works with milliseconds since epoch, not seconds
        document.write(d);
</script>

This Snippet returns:
Thu Apr 12 1956 00:00:00 GMT+0200 (CET)

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 [2016-04-01 16:01 UTC] derick@php.net
-Status: Open +Status: Not a bug
 [2016-04-01 16:01 UTC] derick@php.net 
The correct result is "1956-04-11 23:00:00". Germany did not use summer time until 1980:

Europe/Berlin  Sun Apr 10 00:59:59 1949 UT = Sun Apr 10 01:59:59 1949 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Apr 10 01:00:00 1949 UT = Sun Apr 10 03:00:00 1949 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Oct  2 00:59:59 1949 UT = Sun Oct  2 02:59:59 1949 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Oct  2 01:00:00 1949 UT = Sun Oct  2 02:00:00 1949 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Apr  6 00:59:59 1980 UT = Sun Apr  6 01:59:59 1980 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Apr  6 01:00:00 1980 UT = Sun Apr  6 03:00:00 1980 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Sep 28 00:59:59 1980 UT = Sun Sep 28 02:59:59 1980 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Sep 28 01:00:00 1980 UT = Sun Sep 28 02:00:00 1980 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Mar 29 00:59:59 1981 UT = Sun Mar 29 01:59:59 1981 CET isdst=0 gmtoff=3600
Europe/Berlin  Sun Mar 29 01:00:00 1981 UT = Sun Mar 29 03:00:00 1981 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Sep 27 00:59:59 1981 UT = Sun Sep 27 02:59:59 1981 CEST isdst=1 gmtoff=7200
Europe/Berlin  Sun Sep 27 01:00:00 1981 UT = Sun Sep 27 02:00:00 1981 CET isdst=0 gmtoff=3600

It outputs the same on the shell as in PHP too:

derick@whisky:~ $ TZ=Europe/Berlin date --date "@-433044000"
Wed 11 Apr 23:00:00 CET 1956


The output in javascript also makes no sense, as "Thu Apr 12 1956 00:00:00 GMT+0200 (CET)" uses "+0200" for CET, but that's really supposed to be CEST.
 [2016-04-01 18:24 UTC] snoopyf at gmx dot net 
Yeah, u r right, for Germany summertime is since 1980, getted that wrong.

Then it's JavaScript which makes the mistake in your opinion? Till now I tested the JavaScript Snippet on the current Versions of Firefox and Chrome under Linux and IE11 under Windows... 
Each and every Browser/JavaScript says, that -433044000 is 2016-04-12 00:00:00

So who sais the truth now?
 [2016-04-04 14:02 UTC] derick@php.net 
From what I understand Windows doesn't keep track of historical timezone rules, so that could be an issue here. I have just tested the JavaScript snippet too, and I get the wrong result on Linux/Firefox too. PHP (and the shell) definitely get it right.
 
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