wip: Use UTC internally

According to https://dev.mysql.com/doc/refman/8.0/en/time-zone-support.html

> MySQL converts `TIMESTAMP` values from the current time zone to UTC for storage, and back from UTC to the current time zone for retrieval. (This does not occur for other types such as `DATETIME`.)

That is bad.

- [ ] Check that we do not use TIMESTAMP anywhere or set MySQL timezone to UTC.
- [ ] Verify that PostgreSQL includes timezone offsets when selecting datetime values with timezone.
- [ ] Check that MySQL correctly compares datetimes in db with values containing tz offset as produced by `daos\mysql\statements::datetime()`.
- [ ] Add migrations for sqlite local → UTC when `date.timezone` is not UTC.

src/controllers/Items/Sync.php

@@ -49,8 +49,8 @@ public function sync(): void {
             $this->view->jsonError(['sync' => 'missing since argument']);
         }
 
-        $since = new \DateTimeImmutable($params['since']);
-        $since = $since->setTimeZone(new \DateTimeZone(date_default_timezone_get()));
+        // The client should include a timezone offset but let’s default to UTC in case it does not.
+        $since = new \DateTimeImmutable($params['since'], new \DateTimeZone('UTC'));
 
         $lastUpdate = $this->itemsDao->lastUpdate();
 
@@ -66,9 +66,7 @@ public function sync(): void {
                     $sinceId = $this->itemsDao->lowestIdOfInterest() - 1;
                     // only send 1 day worth of items
                     $notBefore = new \DateTimeImmutable();
-                    $notBefore = $notBefore->setTimeZone(new \DateTimeZone(date_default_timezone_get()));
                     $notBefore = $notBefore->sub(new \DateInterval('P1D'));
-                    $notBefore = $notBefore->setTimeZone(new \DateTimeZone(date_default_timezone_get()));
                 }
 
                 $itemsHowMany = $this->configuration->itemsPerpage;

src/daos/ItemOptions.php

@@ -71,15 +71,17 @@ public static function fromUser(array $data): self {
         }
 
         if (isset($data['fromDatetime']) && is_string($data['fromDatetime']) && strlen($data['fromDatetime']) > 0) {
-            $options->fromDatetime = new \DateTimeImmutable($data['fromDatetime']);
+            // The client should include a timezone offset but let’s default to UTC in case it does not.
+            $options->fromDatetime = new \DateTimeImmutable($data['fromDatetime'], new \DateTimeZone('UTC'));
         }
 
         if (isset($data['fromId']) && is_numeric($data['fromId'])) {
             $options->fromId = (int) $data['fromId'];
         }
 
         if (isset($data['updatedsince']) && is_string($data['updatedsince']) && strlen($data['updatedsince']) > 0) {
-            $options->updatedSince = new \DateTimeImmutable($data['updatedsince']);
+            // The client should include a timezone offset but let’s default to UTC in case it does not.
+            $options->updatedSince = new \DateTimeImmutable($data['updatedsince'], new \DateTimeZone('UTC'));
         }
 
         if (isset($data['tag']) && is_string($data['tag']) && strlen($tag = trim($data['tag'])) > 0) {

src/daos/mysql/Items.php

@@ -569,7 +569,9 @@ public function lastUpdate(): ?DateTimeImmutable {
             FROM ' . $this->configuration->dbPrefix . 'items;');
         $lastUpdate = $res[0]['last_update_time'];
 
-        return $lastUpdate !== null ? new DateTimeImmutable($lastUpdate) : null;
+        // MySQL and SQLite do not support timezones, load it as UTC.
+        // PostgreSQL will include the timezone offset as the part of the returned value and it will take precedence.
+        return $lastUpdate !== null ? new DateTimeImmutable($lastUpdate, new \DateTimeZone('UTC')) : null;
     }
 
     /**
@@ -627,7 +629,8 @@ public function bulkStatusUpdate(array $statuses): void {
 
                     // sanitize update time
                     if (array_key_exists('datetime', $status)) {
-                        $updateDate = new \DateTimeImmutable($status['datetime']);
+                        // The client should include a timezone offset but let’s default to UTC in case it does not.
+                        $updateDate = new \DateTimeImmutable($status['datetime'], new \DateTimeZone('UTC'));
                     } else {
                         $updateDate = null;
                     }

src/daos/mysql/Statements.php

@@ -177,7 +177,8 @@ public static function ensureRowTypes(array $rows, array $expectedRowTypes): arr
                             }
                             break;
                         case DatabaseInterface::PARAM_DATETIME:
-                            $value = new \DateTimeImmutable($row[$columnIndex]);
+                            // MySQL and SQLite do not support timezones, load it as UTC.
+                            $value = new \DateTimeImmutable($row[$columnIndex], new \DateTimeZone('UTC'));
                             break;
                         default:
                             $value = null;

src/daos/pgsql/Statements.php

@@ -104,6 +104,7 @@ public static function ensureRowTypes(array $rows, array $expectedRowTypes): arr
                             }
                             break;
                         case DatabaseInterface::PARAM_DATETIME:
+                            // PostgreSQL will include the timezone offset as the part of the returned value.
                             $value = new \DateTimeImmutable($row[$columnIndex]);
                             break;
                         default:

src/daos/sqlite/Statements.php

@@ -50,14 +50,10 @@ public static function bool(bool $bool): string {
      * @return string representation of datetime
      */
     public static function datetime(\DateTimeImmutable $date): string {
-        // SQLite does not support timezones.
-        // The client previously sent the local timezone
-        // but now it sends UTC time so we need to adjust it here
-        // to avoid fromDatetime mismatch.
-        // TODO: Switch to UTC everywhere.
-        $date = $date->setTimeZone((new \DateTimeImmutable())->getTimeZone());
+        // SQLite does not support timezones so we store all dates in UTC.
+        $utcDate = $date->setTimeZone(new \DateTimeZone('UTC'));
 
-        return $date->format('Y-m-d H:i:s');
+        return $utcDate->format('Y-m-d H:i:s');
     }
 
     /**