More explicit error on date() with convert: false

Fixes #919.

Author: Marsup

lib/date.js

@@ -41,6 +41,9 @@ internals.Date.prototype._base = function (value, state, options) {
     if (result.value instanceof Date && !isNaN(result.value.getTime())) {
         result.errors = null;
     }
+    else if (!options.convert) {
+        result.errors = this.createError('date.strict', null, state, options);
+    }
     else {
         let type;
         if (internals.isIsoDate(this._flags.format)) {

lib/language.js

@@ -55,6 +55,7 @@ exports.errors = {
     },
     date: {
         base: 'must be a number of milliseconds or valid date string',
+        strict: 'must be a valid date',
         min: 'must be larger than or equal to "{{limit}}"',
         max: 'must be less than or equal to "{{limit}}"',
         isoDate: 'must be a valid ISO 8601 date',

test/date.js

@@ -57,7 +57,7 @@ describe('date', () => {
         Joi.date().options({ convert: false }).validate('1-1-2013 UTC', (err, value) => {
 
             expect(err).to.exist();
-            expect(err.message).to.equal('"value" must be a number of milliseconds or valid date string');
+            expect(err.message).to.equal('"value" must be a valid date');
             done();
         });
     });