Use Locale.ENGLISH when parsing dates in Converter.DATE (#426)

* parse Converter.DATE with default locale, fall back to Locale.ENGLISH

* No copy-pasta.

---------

Co-authored-by: Gary Gregory <garydgregory@users.noreply.github.com>

Author: rootvector2

src/main/java/org/apache/commons/cli/Converter.java

@@ -24,6 +24,7 @@ Licensed to the Apache Software Foundation (ASF) under one or more
 import java.nio.file.Paths;
 import java.text.SimpleDateFormat;
 import java.util.Date;
+import java.util.Locale;
 
 /**
  * The definition of the functional interface to call when doing a conversion. Like {@code Function<String,T>} but can throw an Exception.
@@ -76,7 +77,16 @@ public interface Converter<T, E extends Exception> {
     /**
      * Converts a String to a {@link Date} using the format string Form "EEE MMM dd HH:mm:ss zzz yyyy".
      */
-    Converter<Date, java.text.ParseException> DATE = s -> new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy").parse(s);
+    Converter<Date, java.text.ParseException> DATE = s -> {
+        final String pattern = "EEE MMM dd HH:mm:ss zzz yyyy";
+        try {
+            return new SimpleDateFormat(pattern).parse(s);
+        } catch (final java.text.ParseException e) {
+            // Date.toString() always emits English month/day names, so fall back to Locale.ENGLISH
+            // when the default locale rejects the documented format.
+            return new SimpleDateFormat(pattern, Locale.ENGLISH).parse(s);
+        }
+    };
 
     /**
      * Applies the conversion function to the String argument.

src/test/java/org/apache/commons/cli/ConverterTests.java

@@ -27,6 +27,7 @@ Licensed to the Apache Software Foundation (ASF) under one or more
 import java.util.ArrayList;
 import java.util.Date;
 import java.util.List;
+import java.util.Locale;
 import java.util.stream.Stream;
 
 import org.junit.jupiter.api.Test;
@@ -93,6 +94,16 @@ void testDateLocaleDe() throws Exception {
         assertEquals(expected, Converter.DATE.apply(formatted));
     }
 
+    @Test
+    @DefaultLocale(language = "de", country = "DE")
+    void testDateLocaleDeEnglishInput() throws Exception {
+        // Date.toString() always emits English month/day names, so the converter must still parse
+        // them when the default locale is not English.
+        final Date expected = new Date(1023400137000L);
+        final String formatted = new SimpleDateFormat("EEE MMM dd HH:mm:ss zzz yyyy", Locale.ENGLISH).format(expected);
+        assertEquals(expected, Converter.DATE.apply(formatted));
+    }
+
     @Test
     void testFile() throws Exception {
         final URL url = this.getClass().getClassLoader().getResource("./org/apache/commons/cli/existing-readable.file");