PHP日期间隔错误与夏令时

Question

I've come across an issue when trying to calculate the amount of days between two dates. If the start date is before a daylight savings switch, the amount of days is calculated incorrectly.

Below is a quick test to reproduce the error:

/**
 * @dataProvider daysProvider
 */
public function testDays($start, $end, $expectedDays)
{
    $startDate = new \DateTime($start);
    $endDate = new \DateTime($end);
    $interval = $startDate->diff($endDate);
    $this->assertEquals($expectedDays, $interval->format('%a'));
}

/**
 * @dataProvider daysProvider
 */
public function testDaysSydney($start, $end, $expectedDays)
{
    $startDate = new \DateTime($start);
    $endDate = new \DateTime($end);
    $startDate->setTimezone(new \DateTimeZone('Australia/Sydney'));
    $endDate->setTimezone(new \DateTimeZone('Australia/Sydney'));
    $interval = $startDate->diff($endDate);
    $this->assertEquals($expectedDays, $interval->format('%a'));
}

public function daysProvider()
{
    return [
        ['2016-03-01', '2016-03-04', 3],
        ['2016-04-01', '2016-04-04', 3],
    ];
}

And the output:

PHPUnit 6.5.5 by Sebastian Bergmann and contributors.

...F

Time: 23 ms, Memory: 4.00MB

There was 1 failure:

1) TimingTest::testDaysSydney with data set #1 ('2016-04-01', '2016-04-04', 3)
Failed asserting that '2' matches expected 3.

I did find this Bug report: https://bugs.php.net/bug.php?id=63953 but apparently the issue is supposed to be fixed.

Any idea of a workaround for this? Thanks

Answer 1

There is a difference between setting DateTimeZone via DateTime setter method (setTimezone) and setting it via DateTime constructor (as stated in this question). Try to set timezone via constructor:

public function testDaysSydney($start, $end, $expectedDays)
{
    $tz=new \DateTimeZone('Australia/Sydney');
    $startDate = new \DateTime($start, $tz);
    $endDate = new \DateTime($end, $tz);
    $interval = $startDate->diff($endDate);
    $this->assertEquals($expectedDays, $interval->format('%a'));
}