PHP simulate Day Light Savings - php

Question

I have some code that handles dates and times. I think it's OK, but want to test that it works when the clocks go forwards for DST.
I can change the timezone using date_default_timezone_set('Europe/London');, and wondered if there is an easy to simulate being in DST without having to wait till the clocks change!

Answer 1

You don't provide details on what you want to test but I assume you have functions to do time-related stuff, e.g.:
function setExpiryTime(DateTime $start, $minutes){
}
The obvious test is to provide input parameters that will make your code cross DST boundaries. You can either find such information in your favourite search engine or run a simple PHP snippet:
<?php
$timezone = new DateTimeZone('Europe/London');
print_r( $timezone->getTransitions(mktime(0, 0, 0, 1, 1, date('Y')), mktime(0, 0, 0, 12, 31, date('Y'))) );
Array
(
[0] => Array
(
[ts] => 1388530800
[time] => 2013-12-31T23:00:00+0000
[offset] => 0
[isdst] =>
[abbr] => GMT
)
[1] => Array
(
[ts] => 1396141200
[time] => 2014-03-30T01:00:00+0000
[offset] => 3600
[isdst] => 1
[abbr] => BST
)
[2] => Array
(
[ts] => 1414285200
[time] => 2014-10-26T01:00:00+0000
[offset] => 0
[isdst] =>
[abbr] => GMT
)
)
Thus you can test:
setExpiryTime(new DateTime('2014-03-30T00:55:00+0000'), 10);
setExpiryTime(new DateTime('2014-10-26T00:55:00+0000'), 10);

Answer 2

you can certainly find out, whether user is in Daylight saving zone or daylight saving is currently in effect.
echo date('I', time());
This returns 0/1; where,
0 = Daylight saving is not in effect.
1 = Daylight saving is in effect.
more details : http://php.net/manual/en/function.date.php
Based on this result you can make conditional code to simulate your output.