Date 0000-01-01 is valid [Closes #402]

Author: dg

src/Dibi/Result.php

@@ -489,7 +489,7 @@ private function normalize(array &$row): void
 				$row[$key] = ((bool) $value) && $value !== 'f' && $value !== 'F';
 
 			} elseif ($type === Type::DATETIME || $type === Type::DATE || $type === Type::TIME) {
-				if ($value && substr((string) $value, 0, 3) !== '000') { // '', null, false, '0000-00-00', ...
+				if ($value && substr((string) $value, 0, 7) !== '0000-00') { // '', null, false, '0000-00-00', ...
 					$value = new DateTime($value);
 					$row[$key] = $format ? $value->format($format) : $value;
 				} else {

src/Dibi/Row.php

@@ -37,7 +37,7 @@ public function asDateTime(string $key, string $format = null)
 	{
 		$time = $this[$key];
 		if (!$time instanceof DateTime) {
-			if (!$time || substr((string) $time, 0, 3) === '000') { // '', null, false, '0000-00-00', ...
+			if (!$time || substr((string) $time, 0, 7) === '0000-00') { // '', null, false, '0000-00-00', ...
 				return null;
 			}
 			$time = new DateTime($time);