date: Fix unit tests

This fixes is the test case to pass the tests in your own environment. Currently tests for date result on my box is just below.

```
[okuryu.local] (yui3@master) $ yeti src/date/tests/unit/*.html
  Agent connected: Chrome (25.0.1364.172) / Mac OS from 127.0.0.1
✓ Testing started on Chrome (25.0.1364.172) / Mac OS
✗ Date on Chrome (25.0.1364.172) / Mac OS
   in Date Format U.S. Tests
     testUS: Expected %r format.
       Expected: 08:24:00 AM (string)
       Actual: 08:24:00 PM (string)
   in Date Format French Tests
     testFrench: Expected %r format.
       Expected: 08:24:00 AM (string)
       Actual: 08:24:00 PM (string)
   in Date Format Korean Tests
     testKorean: Expected %r format.
       Expected: 08:24:00 오전 (string)
       Actual: 08:24:00 오후 (string)
   in Date Format Punjabi Tests
     testPunjabi: Expected %r format.
       Expected: 08:24:00 ਸਵੇਰੇ (string)
       Actual: 08:24:00 ਸ਼ਾਮ (string)
   in Date Format Tests
     testFormats: Expected %R format.
       Expected: 08:24 (string)
       Actual: 20:24 (string)

✓ Agent completed: Chrome (25.0.1364.172) / Mac OS
✗ Failures: 5 of 22 tests failed. (1.74 seconds)
```

My guess is that it be attributed to the difference of time zone.

```
[okuryu.local] (yui3@fix-date-tests) $ node
> new Date(819199440000)
Sun Dec 17 1995 20:24:00 GMT+0900 (JST)
>
```

So I think that all tests should pass independently of the environment.