Arithmétique avec DateTime

    Les exemples suivants montrent quelques pièges de l'arithmétique de DateTime en ce qui concerne les transitions DST et les mois ayant un nombre différent de jours.

    Exemple #1 DateTimeImmutable::add/sub ajout d'un interval de temps écoulé.

    Ajouter PT24H au dela d'une transition DST semblera ajouter 23/25 heures (pour la plupart des fuseaux horaires).

    <?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;
    ?>

    L'exemple ci-dessus va afficher :

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

    Exemple #2 DateTimeImmutable::modify et strtotime incrémentation ou décrémentation de valeurs individuelles

    Ajouter +24 heures au dela d'une transition DST peut ajouter exactement 24 heures comme vu avec la chaîne date/time (sauf si l'heure de début ou de fin est sur un point de transition).

    <?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;
    ?>

    L'exemple ci-dessus va afficher :

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

    Exemple #3 L'ajout ou la soustraction de dates/heures peut dépasser (en plus ou en moins) des dates

    Comme pour 31 Janvier + 1 mois donnera comme résultat 2 Mars (année bisextile) ou 3 Mars (année normale).

    <?php
    echo "Normal year:\n"; // February has 28 days
    $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"; // February has 29 days
    $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;
    ?>

    L'exemple ci-dessus va afficher :

    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

    Pour obtenir le dernier du mois prochain (autrement dit pour prévenir le dépassement), le format last day of est disponible.

    <?php
    echo "Normal year:\n"; // February has 28 days
    $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"; // February has 29 days
    $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;
    ?>

    L'exemple ci-dessus va afficher :

    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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    User Contributed Notes 1 note

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    laurent dot payetFORBOTS at FORBOTSsupervan dot fr
    5 months 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 explicitelyecho (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 < correctecho 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 $endDatetime->format('c').PHP_EOL;// 2025-03-30T01:58:00+01:00 < correct// 2025-03-30T03:02:00+02:00 < correctecho PHP_EOL;// DST timezone shift is applied improperly when subtracting a duration$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 !!!
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