Fix cant get right format chinese date format error

modify preg expression in NumberFormat.php

[DBNum1][$-804]yyyy"年"m"月"d"日";@
[DBNum1][$-804]yyyy"年"m"月";@
[DBNum1][$-804]m"月"d"日";@

FIX #44

src/PhpSpreadsheet/Style/NumberFormat.php

@@ -464,7 +464,8 @@ class NumberFormat extends Supervisor implements \PhpOffice\PhpSpreadsheet\IComp
         // strip off first part containing e.g. [$-F800] or [$USD-409]
         // general syntax: [$<Currency string>-<language info>]
         // language info is in hexadecimal
-        $format = preg_replace('/^(\[\$[A-Z]*-[0-9A-F]*\])/i', '', $format);
+        // strip off chinese part like [DBNum1][$-804]
+        $format = preg_replace('/^(\[[0-9A-Za-z]*\])*(\[\$[A-Z]*-[0-9A-F]*\])/i', '', $format);
 
         // OpenOffice.org uses upper-case number formats, e.g. 'YYYY', convert to lower-case;
         //    but we don't want to change any quoted strings

tests/data/Style/NumberFormatDates.php

@@ -36,4 +36,20 @@ return [
         '"y-m-d "yyyy-mm-dd" h:m:s "hh:mm:ss',
         'y-m-d 1960-12-19 h:m:s 01:30:00',
     ],
+    // Chinese date format
+    [
+        22269.0625,
+        '[DBNum1][$-804]yyyy"年"m"月"d"日";@',
+        '1960年12月19日',
+    ],
+    [
+        22269.0625,
+        '[DBNum1][$-804]yyyy"年"m"月";@',
+        '1960年12月',
+    ],
+    [
+        22269.0625,
+        '[DBNum1][$-804]m"月"d"日";@',
+        '12月19日',
+    ],
 ];