PHP Date / GMT Weirdness

Question

Either I'm losing my mind, or I've not got the faintest idea what I'm doing. I'm leaning towards the latter.

I'm trying to convert this: 1316826000, which I'm pretty confident should be Sat, 24 Sep 2011 01:00:00 GMT

http://www.onlineconversion.com/unix_time.htm confirms this.

http://www.unixtimestamp.com/index.php tells me 09 / 23 / 11 @ 8:00:00pm EST, so far so good. I happen to be in EST, this is the result I'd like to get back from PHP.

When I do date('l, M d, Y, h:ia', $iTime), I get: Friday, Sep 23, 2011, 12:00am, a full 20 hours off.

I've confirmed the server's time is correct using date('c'). date('c') output is: 2012-05-19T03:19:20+00:00. The server is in the central time zone, where it is currently 10:20pm. May 18.

echo date_default_timezone_get() outputs "GMT" (set somewhere else in the script using date_default_timezone_set('GMT'))

What am I missing? Nothing I've read so far can explain how I'm getting a result 20 hours behind what it should be. Were it an hour fast or slow, I could at least wrap my head around it being some sort of DST idiotry, but 20? Crazyness! Thanks for reading!

Answer 1

Check what your php.ini says for date.timezone. In unix it is usually here: /etc/php.ini Then use a proper timezone recognized by PHP: http://www.php.net/manual/en/timezones.php

date.timezone = 'America/New_York'

Then reload your web server.

Unix time just means the number of seconds since epoch. Has nothing to do with timezones. Timezones simply add or subtract 1 hour (3600 seconds) from the unix time for each zone you move away from GMT. An example:

$userTimezone = new DateTimeZone('America/New_York');
$gmtTimezone = new DateTimeZone('GMT');
$myDateTime = new DateTime('2014-01-22 11:44', $gmtTimezone);
$offset = $userTimezone->getOffset($myDateTime);
echo $offset;

That will output: -14400 or 4 hours. Which is the difference between New York and GMT

Answer 2

Using some Java code with the Joda-Time 2.3 library, as I don't know PHP…

long m = 1316826000L;

DateTime dateTimeUtc = new DateTime( m * 1000L, DateTimeZone.UTC );
DateTime dateTimeNewYork = dateTimeUtc.toDateTime( DateTimeZone.forID( "America/New_York" ) );

System.out.println( "dateTimeUtc: " + dateTimeUtc );
System.out.println( "dateTimeNewYork: " + dateTimeNewYork );

I can tell you that 1316826000 seconds from the beginning of 1970 UTC/GMT (Unix Epoch) is…

dateTimeUtc: 2011-09-24T01:00:00.000Z
dateTimeNewYork: 2011-09-23T21:00:00.000-04:00

So, as the commenter stated, it would be 8 PM in EST but EST was not in effect on that day. DST (Daylight Saving Time) (idiocy, as you correctly noted) was in effect until November 9 of that year (2011). So the time of day is pushed forward one hour, to 9 PM.

In GMT/UTC, that means 1 AM in the morning of the next day.

Standard time in east coast US is 5 hours behind UTC/GMT. With DST it is 4 hours behind UTC/GMT (one hour closer).

Where you got confused:

• Your time format/conversion in incorrect.
  I can't help with that as I don't know PHP.
• You should be using a competent date-time library for this kind of work.
  Date-time work is complicated, tricky, confusing, and error-prone.
  This question discusses possibilities of Joda-Time (for Java) sorts of libraries for PHP.
• You used three-letter time zone codes. Avoid these.
  Those codes are neither standardized nor unique -- there are common duplicates. Instead, use proper time zone names. In your case of east coast US, "America/New_York". Furthermore, in this case you confused the time zone area and rules (east coast US) with a particular application of those rules (EST). Saying "America/New_York" means "whatever time zone rules were in effect on that date, whereas saying "EST" (if interpreted to mean Eastern Standard Time in US) means "UTC-05:00". So either (a) use a time zone name such as "America/New_York", or (b) use a specific offset such as "-05:00".