Pass the input buffer to the validation function. This can be picked up in the validator todo validation beyond the mask definition.

Also extended the date validation in jquery.inputmask.extentions.
Validation for leap years will be added tomorrow.

jquery.inputmask.extentions.js

@@ -8,11 +8,55 @@ Optional extentions on the jquery.inputmask base
 */
 (function($){
 $.extend($.inputmask.defaults.aliases, {
-    'date': {
-        mask: "d/m/y"
-    },
     'dd/mm/yyyy': {
-        alias: "date"
+        mask: "d/m/y",
+        definitions: {
+                    'm': { //month
+                        "validator": function(chrs, buffer) { 
+                        				var dayValue = buffer.join('').substr(0, 3);
+                        				return new RegExp("((0[1-9]|[12][0-9])\/(0[1-9]|1[012]))|(30\/(0[13-9]|1[012]))|(31\/(0[13578]|1[02]))").test(dayValue + chrs); },
+                        "cardinality": 2,
+                        "prevalidator": [{ "validator": "[01]", "cardinality": 1}]
+                    },
+                    'y': { //year
+                        "validator": "(19|20)\\d\\d",
+                        "cardinality": 4,
+                        "prevalidator": [
+                        { "validator": "[12]", "cardinality": 1 },
+                        { "validator": "(19|20)", "cardinality": 2 },
+                        { "validator": "(19|20)\\d", "cardinality": 3 }
+                        ]
+                    }
+        },
+        insertMode: false 
+    }, 
+    'mm/dd/yyyy': {
+        mask: "m/d/y",
+        definitions: {
+                    'd': { //day
+                        "validator": function(chrs, buffer) { 
+                        				var monthValue = buffer.join('').substr(0, 3);
+                        				return new RegExp("((0[1-9]|1[012])\/(0[1-9]|[12][0-9]))|((0[13-9]|1[012])\/30)|((0[13578]|1[02])\/31)").test(monthValue + chrs); },
+                        "cardinality": 2,
+                        "prevalidator": [{ "validator": function(chrs, buffer) { 
+                        									var monthValue = buffer.join('').substr(0, 3);
+                        									return new RegExp("((0[13-9]|1[012])\/[0-3])|(02\/[0-2])").test(monthValue + chrs); },
+                        				 "cardinality": 1}]
+                    },
+                    'y': { //year
+                        "validator": "(19|20)\\d\\d",
+                        "cardinality": 4,
+                        "prevalidator": [
+                        { "validator": "[12]", "cardinality": 1 },
+                        { "validator": "(19|20)", "cardinality": 2 },
+                        { "validator": "(19|20)\\d", "cardinality": 3 }
+                        ]
+                    }
+        },
+        insertMode: false 
+    }, 
+    'date': {
+        alias: "dd/mm/yyyy"
     },
     'hh:mm:ss': {
         mask: "h:s:s",

jquery.inputmask.js

@@ -3,7 +3,7 @@ Input Mask plugin for jquery
 http://github.com/RobinHerbots/jquery.inputmask
 Copyright (c) 2010 Robin Herbots
 Licensed under the MIT license (http://www.opensource.org/licenses/mit-license.php)
-Version: 0.4.3a
+Version: 0.4.3b
  
 This plugin is based on the masked input plugin written by Josh Bush (digitalbush.com)
 */
@@ -23,7 +23,7 @@ This plugin is based on the masked input plugin written by Josh Bush (digitalbus
                 oncomplete: null, //executes when the mask is complete
                 oncleared: null, //executes when the mask is cleared
                 repeat: 0, //repetitions of the mask
-                greedy: true, //true: allocated buffer for the mask a repetitions - false: allocate only if needed
+                greedy: true, //true: allocated buffer for the mask and repetitions - false: allocate only if needed
                 patch_val: true, //override the jquery.val fn to detect changed in the inputmask by setting val(value)
                 autoUnmask: false, //in combination with patch_val: true => automatically unmask when retrieving the value with $.fn.val
                 numericInput: false, //numericInput input direction style (input shifts to the left while holding the caret position)
@@ -75,7 +75,7 @@ This plugin is based on the masked input plugin written by Josh Bush (digitalbus
         };
 
         $.fn.inputmask = function(fn, options) {
-            var opts = $.extend({}, $.inputmask.defaults, options);
+            var opts = $.extend(true, {}, $.inputmask.defaults, options);
             var pasteEventName = $.browser.msie ? 'paste.inputmask' : 'input.inputmask';
             var iPhone = (window.orientation != undefined);
 
@@ -163,7 +163,7 @@ This plugin is based on the masked input plugin written by Josh Bush (digitalbus
                         break;
                 }
             } if (typeof fn == "object") {
-                opts = $.extend({}, $.inputmask.defaults, fn);
+                opts = $.extend(true, {}, $.inputmask.defaults, fn);
 
                 //init buffer
                 var _buffer = getMaskTemplate();
@@ -179,7 +179,7 @@ This plugin is based on the masked input plugin written by Josh Bush (digitalbus
                 var aliasDefinition = opts.aliases[aliasStr];
                 if (aliasDefinition)
                    if(!aliasDefinition.alias) {
-                     $.extend(opts, aliasDefinition);  //merge alias definition in the options
+                     $.extend(true, opts, aliasDefinition);  //merge alias definition in the options
                      return true;
                    } else return ResolveAlias(aliasDefinition.alias); //alias is another alias
                 return false;
@@ -262,7 +262,7 @@ This plugin is based on the masked input plugin written by Josh Bush (digitalbus
                 }
 
                 if (c) { chrs += c; }
-                return tests[testPos].fn != null ? tests[testPos].fn.test(chrs) : false;
+                return tests[testPos].fn != null ? tests[testPos].fn.test(chrs, buffer) : false;
             }
 
             function isMask(pos) {