util: fix invalid date output with util.inspect

Prevent util.inspect of throwing on date object with invalid date value.
It changed to output result of toString method call.

PR-URL: https://github.com/nodejs/node/pull/6504
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Evan Lucas <evanlucas@me.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/util.js

@@ -348,7 +348,11 @@ function formatValue(ctx, value, recurseTimes) {
       return ctx.stylize(RegExp.prototype.toString.call(value), 'regexp');
     }
     if (isDate(value)) {
-      return ctx.stylize(Date.prototype.toISOString.call(value), 'date');
+      if (Number.isNaN(value.getTime())) {
+        return ctx.stylize(value.toString(), 'date');
+      } else {
+        return ctx.stylize(Date.prototype.toISOString.call(value), 'date');
+      }
     }
     if (isError(value)) {
       return formatError(value);

test/parallel/test-util-inspect.js

@@ -12,8 +12,9 @@ assert.equal(util.inspect(function() {}), '[Function]');
 assert.equal(util.inspect(undefined), 'undefined');
 assert.equal(util.inspect(null), 'null');
 assert.equal(util.inspect(/foo(bar\n)?/gi), '/foo(bar\\n)?/gi');
-assert.equal(util.inspect(new Date('Sun, 14 Feb 2010 11:48:40 GMT')),
+assert.strictEqual(util.inspect(new Date('Sun, 14 Feb 2010 11:48:40 GMT')),
   new Date('2010-02-14T12:48:40+01:00').toISOString());
+assert.strictEqual(util.inspect(new Date('')), (new Date('')).toString());
 
 assert.equal(util.inspect('\n\u0001'), "'\\n\\u0001'");