fix(datepicker): min-date validation is incorrect in GMT+X timezones

Fixes #11963

Author: Splaktar

package.json

@@ -133,4 +133,4 @@
     "node": ">=10",
     "npm": ">=6"
   }
-}
+}

src/components/datepicker/js/dateUtil.js

@@ -310,8 +310,8 @@
      }
 
     /**
-     * @param {Date} value
-     * @return {boolean|boolean}
+     * @param {Date} value date in local timezone
+     * @return {Date} date with local timezone removed
      */
     function removeLocalTzAndReparseDate(value) {
       var dateValue, formattedDate;

src/components/datepicker/js/datepickerDirective.js

@@ -1001,7 +1001,7 @@
     var self = this;
     var timezone = this.$mdUtil.getModelOption(this.ngModelCtrl, 'timezone');
 
-    if (this.dateUtil.isValidDate(value)) {
+    if (this.dateUtil.isValidDate(value) && timezone != null) {
       this.date = this.dateUtil.removeLocalTzAndReparseDate(value);
     } else {
       this.date = value;