PHP: 日期/时间算法

日期/时间算法

以下示例展示了有关 DST 转换和具有不同天数的月份的日期/时间算法的一些缺陷。

示例 #1 DateTimeImmutable::add/sub 添加包含经过时间的间隔

在 DST 转换上添加 PT24H 似乎会增加 23/25 小时（大多数时区）。

<?php
$dt = new DateTimeImmutable("2015-11-01 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->add(new DateInterval("PT3H"));
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
?>

以上示例会输出：

Start: 2015-11-01 00:00:00 -04:00
End:   2015-11-01 02:00:00 -05:00

示例 #2 DateTimeImmutable::modify 和 strtotime 递增/减单个组件值

在 DST 转换上添加 +24 小时将准确添加 24 小时，如日期/时间字符串中所示（除非开始/结束时间位于转换点）。

<?php
$dt = new DateTimeImmutable("2015-11-01 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->modify("+24 hours");
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
?>

以上示例会输出：

Start: 2015-11-01 00:00:00 -04:00
End:   2015-11-02 00:00:00 -05:00

示例 #3 新增/减去时间可能会溢出/下溢日期

就像 1 月 31 日 + 1 月会导致 3 月 2 日（闰年）或 3 月 3 日（平年）。

<?php
echo "Normal year:\n"; // 2 月有 28 天
$dt = new DateTimeImmutable("2015-01-31 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->modify("+1 month");
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;

echo "Leap year:\n"; // 2 月有 29 天
$dt = new DateTimeImmutable("2016-01-31 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->modify("+1 month");
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
?>

以上示例会输出：

Normal year:
Start: 2015-01-31 00:00:00 -05:00
End:   2015-03-03 00:00:00 -05:00
Leap year:
Start: 2016-01-31 00:00:00 -05:00
End:   2016-03-02 00:00:00 -05:00

要获取下个月的最后一天（例如防止溢出），可以使用 last day of 格式。

<?php
echo "Normal year:\n"; // 2 月有 28 天
$dt = new DateTimeImmutable("2015-01-31 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->modify("last day of next month");
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;

echo "Leap year:\n"; // 2 月有 29 天
$dt = new DateTimeImmutable("2016-01-31 00:00:00", new DateTimeZone("America/New_York"));
echo "Start: ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
$dt = $dt->modify("last day of next month");
echo "End:   ", $dt->format("Y-m-d H:i:s P"), PHP_EOL;
?>

以上示例会输出：

Normal year:
Start: 2015-01-31 00:00:00 -05:00
End:   2015-02-28 00:00:00 -05:00
Leap year:
Start: 2016-01-31 00:00:00 -05:00
End:   2016-02-29 00:00:00 -05:00

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laurent dot payetFORBOTS at FORBOTSsupervan dot fr ¶

18 hours ago

Be careful when subtracting a duration crossing a DST change, it can output a resulting date AFTER your base date.

// tested in 8.3.18, 7.4.33

// DST timezone shift is applied properly when setting time explicitely

echo (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(1,59,0)->format('c').PHP_EOL;
echo (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(2,0,0)->format('c').PHP_EOL;
echo (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(2,1,0)->format('c').PHP_EOL;

// 2025-03-30T01:59:00+01:00 < correct
// 2025-03-30T03:00:00+02:00 < correct
// 2025-03-30T03:01:00+02:00 < correct

echo PHP_EOL;

// DST timezone shift is applied properly when addind a duration

$startDateTime = (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(1,58,0);
echo $startDateTime->format('c').PHP_EOL;
$endDatetime = clone($startDateTime)->add(DateInterval::createFromDateString('4 minutes'));
echo $endDatetime->format('c').PHP_EOL;

// 2025-03-30T01:58:00+01:00 < correct
// 2025-03-30T03:02:00+02:00 < correct

echo PHP_EOL;

// DST timezone shift is applied improperly when subtracting a duration

$startDateTime = (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(3,2,0);
echo $startDateTime->format('c').PHP_EOL;
$endDatetime = clone($startDateTime)->sub(DateInterval::createFromDateString('4 minutes'));
echo $endDatetime->format('c').PHP_EOL;

// 2025-03-30T03:02:00+02:00 < correct
// 2025-03-30T03:58:00+02:00 < incorrect !!!

echo PHP_EOL;

// DST timezone shift is still applied improperly when adding a negative duration

$startDateTime = (new DateTime('2025-03-30'))->setTimeZone(new DateTimeZone('Europe/Paris'))->setTime(3,2,0);
echo $startDateTime->format('c').PHP_EOL;
$endDatetime = clone($startDateTime)->add(DateInterval::createFromDateString('-4 minutes'));
echo $endDatetime->format('c').PHP_EOL;

// 2025-03-30T03:02:00+02:00 < correct
// 2025-03-30T03:58:00+02:00 < incorrect !!!