Description:
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When initializing two new DateTime objects using equivalent DateTimeZone()'s of US/Central and Etc/GMT-6, the result is incorrect

Reproduce code:
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$objTime = new DateTime('now', new DateTimeZone('US/Central'));
echo $objTime->format('m/d/Y H:i:s T')."\r\n";
$objTime = new DateTime('now', new DateTimeZone('Etc/GMT-6'));
echo $objTime->format('m/d/Y H:i:s T')."\r\n";


Expected result:
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The same timestamp on two lines (with different TimeZone specifiers)

Actual result:
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Different timestamps.