<?php
ini_set('date.timezone', 'Europe/Lisbon');
ini_set('intl.default_locale', 'pt_PT');
$cal = new IntlGregorianCalendar(2013, 6 /* July */, 1, 4, 56, 31);
var_dump($cal->inDaylightTime()); // true
$cal->set(IntlCalendar::FIELD_MONTH, 11 /* December */);
var_dump($cal->inDaylightTime()); // false
//DST end transition on 2013-10-27 at 0200 (wall time back 1 hour)
$cal = new IntlGregorianCalendar(2013, 9 /* October */, 27, 1, 30, 0);
var_dump($cal->inDaylightTime()); // false (default WALLTIME_LAST)
$cal->setRepeatedWallTimeOption(IntlCalendar::WALLTIME_FIRST);
$cal->set(IntlCalendar::FIELD_HOUR_OF_DAY, 1); // force time recalculation
var_dump($cal->inDaylightTime()); // true