Remove most calls to date_default_timezone_* calls

- It was wrongly used to set the node-wide ot user-specific timezone
- It is now fully managed from the App object
- Add a static variable to DateTimeFormat maintain the convenient local() method

src/Util/Temporal.php

@@ -360,23 +360,19 @@ class Temporal
 	 * Returns the age in years, given a date of birth and the timezone of the person
 	 * whose date of birth is provided.
 	 *
-	 * @param string $dob       Date of Birth
-	 * @param string $owner_tz  (optional) Timezone of the person of interest
+	 * @param string $dob      Date of Birth
+	 * @param string $timezone Timezone of the person of interest
 	 *
 	 * @return int Age in years
 	 * @throws \Exception
 	 */
-	public static function getAgeByTimezone($dob, $owner_tz = ''): int
+	public static function getAgeByTimezone(string $dob, string $timezone): int
 	{
 		if (!intval($dob)) {
 			return 0;
 		}
 
-		if (!$owner_tz) {
-			$owner_tz = date_default_timezone_get();
-		}
-
-		$birthdate = new DateTime($dob . ' 00:00:00', new DateTimeZone($owner_tz));
+		$birthdate = new DateTime($dob . ' 00:00:00', new DateTimeZone($timezone));
 		$currentDate = new DateTime('now', new DateTimeZone('UTC'));
 
 		$interval = $birthdate->diff($currentDate);