diff --git a/dist/handlebars-i18n.js b/dist/handlebars-i18n.js
index d8b2a65..8d0bfe3 100644
--- a/dist/handlebars-i18n.js
+++ b/dist/handlebars-i18n.js
@@ -456,6 +456,13 @@
          * @returns {string}
          */
         function (dateInput, offset, unit, options) {
+
+          if (typeof dateInput !== 'number' && typeof dateInput !== 'string')
+            throw new Error('@ handlebars-i18n: invalid first argument "dateInput" was given for _dateAdd.');
+
+          if (typeof offset !== 'number')
+            throw new Error('@ handlebars-i18n: invalid second argument "offset" was given for _dateAdd.');
+
           const date = __createDateObj(dateInput);
 
           unit = unit || 'hour';
diff --git a/test/handlebars-i18n.test.js b/test/handlebars-i18n.test.js
index 85ff469..8864b54 100644
--- a/test/handlebars-i18n.test.js
+++ b/test/handlebars-i18n.test.js
@@ -59,6 +59,10 @@ describe('handlebars-i18n Tests', function () {
     assert.isFunction(hI18n.helpers._date);
   });
 
+  it('after method call init() HandlebarsEnvironment object should have a function _dateAdd', function () {
+    assert.isFunction(hI18n.helpers._dateAdd);
+  });
+
   it('after method call init() HandlebarsEnvironment object should have a function _dateRel', function () {
     assert.isFunction(hI18n.helpers._dateRel);
   });
@@ -256,6 +260,20 @@ describe('handlebars-i18n Tests', function () {
   });
 
 
+  /****************************************
+   Tests against function _date
+   ****************************************/
+
+
+  it('function _dateAdd should return "12/17/1995" when called with parameters "December 17, 1995 02:00:00", 1, and "day"', function () {
+    i18next.changeLanguage('en');
+    const res = hI18n.helpers._dateAdd('December 17, 1995 02:00:00', 1, "day");
+    assert.equal('12/18/1995', res);
+  });
+
+
+
+
   /****************************************
    Tests against function _dateRel
    ****************************************/