diff --git a/php/src/A.php b/php/src/A.php
index 75f0284..dffd3d2 100644
--- a/php/src/A.php
+++ b/php/src/A.php
@@ -218,10 +218,10 @@ class A {
   static final function filter_f($dest): void { self::filter_if($dest, [cv::class, "f"]);}
   static final function filter_pt($dest): void { self::filter_if($dest, [cv::class, "pt"]);}
   static final function filter_pf($dest): void { self::filter_if($dest, [cv::class, "pf"]);}
-  static final function filter_equals($dest, $value): void { self::filter_if($dest, cv::equals($value)); }
-  static final function filter_not_equals($dest, $value): void { self::filter_if($dest, cv::not_equals($value)); }
-  static final function filter_same($dest, $value): void { self::filter_if($dest, cv::same($value)); }
-  static final function filter_not_same($dest, $value): void { self::filter_if($dest, cv::not_same($value)); }
+  static final function filter_equals($dest, $value): void { self::filter_if($dest, cv::Fequals($value)); }
+  static final function filter_not_equals($dest, $value): void { self::filter_if($dest, cv::Fnot_equals($value)); }
+  static final function filter_same($dest, $value): void { self::filter_if($dest, cv::Fsame($value)); }
+  static final function filter_not_same($dest, $value): void { self::filter_if($dest, cv::Fnot_same($value)); }
 
   #############################################################################
 
diff --git a/php/src/cl.php b/php/src/cl.php
index 2c2bac1..f0919ea 100644
--- a/php/src/cl.php
+++ b/php/src/cl.php
@@ -817,10 +817,10 @@ class cl {
   static final function all_f(?array $array): bool { return self::all_if($array, [cv::class, "f"]);}
   static final function all_pt(?array $array): bool { return self::all_if($array, [cv::class, "pt"]);}
   static final function all_pf(?array $array): bool { return self::all_if($array, [cv::class, "pf"]);}
-  static final function all_equals(?array $array, $value): bool { return self::all_if($array, cv::equals($value)); }
-  static final function all_not_equals(?array $array, $value): bool { return self::all_if($array, cv::not_equals($value)); }
-  static final function all_same(?array $array, $value): bool { return self::all_if($array, cv::same($value)); }
-  static final function all_not_same(?array $array, $value): bool { return self::all_if($array, cv::not_same($value)); }
+  static final function all_equals(?array $array, $value): bool { return self::all_if($array, cv::Fequals($value)); }
+  static final function all_not_equals(?array $array, $value): bool { return self::all_if($array, cv::Fnot_equals($value)); }
+  static final function all_same(?array $array, $value): bool { return self::all_if($array, cv::Fsame($value)); }
+  static final function all_not_same(?array $array, $value): bool { return self::all_if($array, cv::Fnot_same($value)); }
 
   #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
@@ -842,10 +842,10 @@ class cl {
   static final function any_f(?array $array): bool { return self::any_if($array, [cv::class, "f"]);}
   static final function any_pt(?array $array): bool { return self::any_if($array, [cv::class, "pt"]);}
   static final function any_pf(?array $array): bool { return self::any_if($array, [cv::class, "pf"]);}
-  static final function any_equals(?array $array, $value): bool { return self::any_if($array, cv::equals($value)); }
-  static final function any_not_equals(?array $array, $value): bool { return self::any_if($array, cv::not_equals($value)); }
-  static final function any_same(?array $array, $value): bool { return self::any_if($array, cv::same($value)); }
-  static final function any_not_same(?array $array, $value): bool { return self::any_if($array, cv::not_same($value)); }
+  static final function any_equals(?array $array, $value): bool { return self::any_if($array, cv::Fequals($value)); }
+  static final function any_not_equals(?array $array, $value): bool { return self::any_if($array, cv::Fnot_equals($value)); }
+  static final function any_same(?array $array, $value): bool { return self::any_if($array, cv::Fsame($value)); }
+  static final function any_not_same(?array $array, $value): bool { return self::any_if($array, cv::Fnot_same($value)); }
 
   #~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   
@@ -876,10 +876,10 @@ class cl {
   static final function filter_f(?array $array): ?array { return self::filter_if($array, [cv::class, "f"]);}
   static final function filter_pt(?array $array): ?array { return self::filter_if($array, [cv::class, "pt"]);}
   static final function filter_pf(?array $array): ?array { return self::filter_if($array, [cv::class, "pf"]);}
-  static final function filter_equals(?array $array, $value): ?array { return self::filter_if($array, cv::equals($value)); }
-  static final function filter_not_equals(?array $array, $value): ?array { return self::filter_if($array, cv::not_equals($value)); }
-  static final function filter_same(?array $array, $value): ?array { return self::filter_if($array, cv::same($value)); }
-  static final function filter_not_same(?array $array, $value): ?array { return self::filter_if($array, cv::not_same($value)); }
+  static final function filter_equals(?array $array, $value): ?array { return self::filter_if($array, cv::Fequals($value)); }
+  static final function filter_not_equals(?array $array, $value): ?array { return self::filter_if($array, cv::Fnot_equals($value)); }
+  static final function filter_same(?array $array, $value): ?array { return self::filter_if($array, cv::Fsame($value)); }
+  static final function filter_not_same(?array $array, $value): ?array { return self::filter_if($array, cv::Fnot_same($value)); }
 
   #############################################################################
 
diff --git a/php/src/cv.php b/php/src/cv.php
index fd61a8e..ac3dbac 100644
--- a/php/src/cv.php
+++ b/php/src/cv.php
@@ -49,7 +49,7 @@ class cv {
    * contruire une fonction qui retourne vrai si on lui passe en argument une
    * valeur égale à $value
    */
-  static final function equals($value): callable {
+  static final function Fequals($value): callable {
     return function ($arg) use($value) { return $arg == $value; };
   }
 
@@ -57,7 +57,7 @@ class cv {
    * contruire une fonction qui retourne vrai si on lui passe en argument une
    * valeur qui n'est pas égale à $value
    */
-  static final function not_equals($value): callable {
+  static final function Fnot_equals($value): callable {
     return function ($arg) use($value) { return $arg != $value; };
   }
 
@@ -65,7 +65,7 @@ class cv {
    * contruire une fonction qui retourne vrai si on lui passe en argument une
    * valeur strictement égale à $value
    */
-  static final function same($value): callable {
+  static final function Fsame($value): callable {
     return function ($arg) use($value) { return $arg === $value; };
   }
 
@@ -73,7 +73,7 @@ class cv {
    * contruire une fonction qui retourne vrai si on lui passe en argument une
    * valeur qui n'est pas strictement égale à $value
    */
-  static final function not_same($value): callable {
+  static final function Fnot_same($value): callable {
     return function ($arg) use($value) { return $arg !== $value; };
   }
 
@@ -231,6 +231,24 @@ class cv {
 
   #############################################################################
 
+  /**
+   * tester l'égalité non stricte de deux valeurs, dans le cas où leurs types ne
+   * sont pas forcément cohérents: par exemple eq("1", 1) === true
+   *
+   * cette fonction est utile par exemple quand on veut comparer des données
+   * provenant d'une base de données: PHP a la facheuse tendance de retourner
+   * les nombres sous forme de chaines
+   */
+  static final function equals($a, $b): bool {
+    # cette fonction existe parce que le type des valeurs retournées par la BDD
+    # n'est pas cohérent, "1" au lieu de 1 par exemple
+    if ($a === null) return $b === null;
+    elseif ($b === null) return $a === null;
+    elseif (is_scalar($a)) return strval($a) === strval($b);
+    # ne pas utiliser l'égalité stricte ici: ce sont des objets
+    else return $a == $b;
+  }
+
   /** retourner -1, 0 ou 1 en fonction de l'ordre relatif entre $a et $b */
   static final function compare($a, $b): int {
     if ($a === $b) return 0;
diff --git a/php/src/db/CapacitorStorage.php b/php/src/db/CapacitorStorage.php
index 232d935..65aa09c 100644
--- a/php/src/db/CapacitorStorage.php
+++ b/php/src/db/CapacitorStorage.php
@@ -3,6 +3,7 @@ namespace nulib\db;
 
 use nulib\A;
 use nulib\cl;
+use nulib\cv;
 use nulib\db\_private\_migration;
 use nulib\php\func;
 use nulib\ValueException;
@@ -479,8 +480,9 @@ abstract class CapacitorStorage {
             # ne jamais mettre à jour la clé primaire
             continue;
           }
-          $pvalue = $praw[$col] ?? null;
-          if ($value !== $pvalue) $updates[$col] = $value;
+          if (!cv::equals($value, $praw[$col] ?? null)) {
+            $updates[$col] = $value;
+          }
         }
         if (count($updates) == 1 && array_key_first($updates) == "modified_") {
           # si l'unique modification porte sur la date de modification, alors
diff --git a/php/src/php/time/DateTime.php b/php/src/php/time/DateTime.php
index f819fe2..438b614 100644
--- a/php/src/php/time/DateTime.php
+++ b/php/src/php/time/DateTime.php
@@ -139,6 +139,12 @@ class DateTime extends \DateTime {
     return false;
   }
 
+  /** retourner le nombre de secondes depuis minuit */
+  static function _nbsecs_format(\DateTime $datetime): string {
+    [$h, $m, $s] = explode(",", $datetime->format("H,i,s"));
+    return $h * 3600 + $m * 60 + $s;
+  }
+
   static function _YmdHMSZ_format(\DateTime $datetime): string {
     $YmdHMS = $datetime->format("Ymd\\THis");
     $Z = $datetime->format("P");
@@ -156,6 +162,7 @@ class DateTime extends \DateTime {
     "second" => "s",
     "wday" => "N",
     "wnum" => "W",
+    "nbsecs" => [self::class, "_nbsecs_format"],
   ];
   const STRING_FORMATS = [
     "timezone" => "P",
@@ -166,14 +173,6 @@ class DateTime extends \DateTime {
     "YmdHMSZ" => [self::class, "_YmdHMSZ_format"],
   ];
 
-  static function clone(DateTimeInterface $dateTime): self {
-    if ($dateTime instanceof static) return clone $dateTime;
-    $clone = new static();
-    $clone->setTimestamp($dateTime->getTimestamp());
-    $clone->setTimezone($dateTime->getTimezone());
-    return $clone;
-  }
-
   /**
    * corriger une année à deux chiffres qui est située dans le passé et
    * retourner l'année à 4 chiffres.
@@ -282,7 +281,7 @@ class DateTime extends \DateTime {
       if ($Y !== null) {
         if ($H === null) $datetime = sprintf("%04d-%02d-%02d", $Y, $m, $d);
         else $datetime = sprintf("%04d-%02d-%02d %02d:%02d:%02d", $Y, $m, $d, $H, $M, $S);
-        if ($Z !== null) $timezone = new DateTimeZone(self::fix_z($Z));
+        if ($Z !== null) $timezone ??= new DateTimeZone(self::fix_z($Z));
       }
       parent::__construct($datetime, $timezone);
 
@@ -295,7 +294,7 @@ class DateTime extends \DateTime {
       } else {
         $datetime = sprintf("%04d-%02d-%02d %02d:%02d:%02d", $Y, $m, $d, $H ?? 0, $M ?? 0, $S ?? 0);
       }
-      if ($Z !== null) $timezone = new DateTimeZone(self::fix_z($Z));
+      if ($Z !== null) $timezone ??= new DateTimeZone(self::fix_z($Z));
       parent::__construct($datetime, $timezone);
 
     } else {
@@ -308,6 +307,10 @@ class DateTime extends \DateTime {
     }
   }
 
+  function clone(): self {
+    return clone $this;
+  }
+
   function diff($target, $absolute=false): DateInterval {
     return new DateInterval(parent::diff($target, $absolute));
   }
@@ -374,7 +377,7 @@ class DateTime extends \DateTime {
   function __get($name) {
     if (array_key_exists($name, self::INT_FORMATS)) {
       $format = self::INT_FORMATS[$name];
-      if (is_callable($format)) return $format($this);
+      if (is_callable($format)) return intval($format($this));
       else return intval($this->format($format));
     } elseif (array_key_exists($name, self::STRING_FORMATS)) {
       $format = self::STRING_FORMATS[$name];
diff --git a/php/src/php/time/Delay.php b/php/src/php/time/Delay.php
index 4afcf37..e773efa 100644
--- a/php/src/php/time/Delay.php
+++ b/php/src/php/time/Delay.php
@@ -40,8 +40,8 @@ class Delay {
     "s" => [1, 0],
   ];
 
-  static function compute_dest(int $x, string $u, ?int $y, DateTime $from): array {
-    $dest = DateTime::clone($from);
+  static function compute_dest(int $x, string $u, ?int $y, ?DateTimeInterface $from): array {
+    $dest = DateTime::with($from)->clone();
     $yu = null;
     switch ($u) {
     case "w":
@@ -92,7 +92,7 @@ class Delay {
   function __construct($delay, ?DateTimeInterface $from=null) {
     if ($from === null) $from = new DateTime();
     if ($delay === "INF") {
-      $dest = DateTime::clone($from);
+      $dest = DateTime::with($from)->clone();
       $dest->add(new DateInterval("P9999Y"));
       $repr = "INF";
     } elseif (is_int($delay)) {
diff --git a/php/tests/php/time/DateTest.php b/php/tests/php/time/DateTest.php
index 857ca33..458e42b 100644
--- a/php/tests/php/time/DateTest.php
+++ b/php/tests/php/time/DateTest.php
@@ -29,7 +29,7 @@ class DateTest extends TestCase {
 
   function testClone() {
     $date = self::dt("now");
-    $clone = Date::clone($date);
+    $clone = $date->clone();
     self::assertInstanceOf(DateTime::class, $clone);
   }
 
diff --git a/php/tests/php/time/DateTimeTest.php b/php/tests/php/time/DateTimeTest.php
index 088bc79..67cc9de 100644
--- a/php/tests/php/time/DateTimeTest.php
+++ b/php/tests/php/time/DateTimeTest.php
@@ -32,13 +32,17 @@ class DateTimeTest extends TestCase {
 
   function testDateTimeZ() {
     $date = new DateTime("20240405T091523Z");
+    self::assertSame("20240405T131523", $date->YmdHMS);
+    self::assertSame("20240405T131523+04:00", $date->YmdHMSZ);
+    # comme on spécifie la timezone, la valeur Z est ignorée
+    $date = new DateTime("20240405T091523Z", new DateTimeZone("Indian/Reunion"));
     self::assertSame("20240405T091523", $date->YmdHMS);
-    self::assertSame("20240405T091523Z", $date->YmdHMSZ);
+    self::assertSame("20240405T091523+04:00", $date->YmdHMSZ);
   }
 
   function testClone() {
     $date = self::dt("now");
-    $clone = DateTime::clone($date);
+    $clone = $date->clone();
     self::assertInstanceOf(DateTime::class, $clone);
   }
 
@@ -51,7 +55,7 @@ class DateTimeTest extends TestCase {
     self::assertSame("05/04/2024 00:00:00", strval(new DateTime("20240405")));
     self::assertSame("05/04/2024 00:00:00", strval(new DateTime("240405")));
     self::assertSame("05/04/2024 09:15:23", strval(new DateTime("20240405T091523")));
-    self::assertSame("05/04/2024 09:15:23", strval(new DateTime("20240405T091523Z")));
+    self::assertSame("05/04/2024 13:15:23", strval(new DateTime("20240405T091523Z")));
     self::assertSame("05/04/2024 09:15:23", strval(new DateTime("5/4/2024 9:15:23")));
     self::assertSame("05/04/2024 09:15:23", strval(new DateTime("5/4/2024 9.15.23")));
     self::assertSame("05/04/2024 09:15:00", strval(new DateTime("5/4/2024 9:15")));