Default to UTC in the legacy date parser.

test/mjsunit/regress/regress-2521.js

Index: test/mjsunit/regress/regress-2521.js
diff --git a/test/mjsunit/regress/regress-crbug-172345.js b/test/mjsunit/regress/regress-2521.js
similarity index 93%
copy from test/mjsunit/regress/regress-crbug-172345.js
copy to test/mjsunit/regress/regress-2521.js
index 711501caa791f2974635ac4dd894568a2e3fc982..55a4b6addbb6dcff27f39e4c1e0f353c9bf8d30a 100644
--- a/test/mjsunit/regress/regress-crbug-172345.js
+++ b/test/mjsunit/regress/regress-2521.js
@@ -25,10 +25,7 @@
 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
-function f(a,i) {
-  return a[i];
-}
+var legacy = new Date("2013-2-31");
+var es5 = new Date("2013-02-31");
+assertEquals(es5.toString(), legacy.toString());
 
-f([1,2,3], "length");
-f([1,2,3], "length");
-f([1,2,3], 2);