Custom Validation Function

Ok now I'm trying to have my function in a helper inside helpers/ folder.
But I'm getting this error

Code:

An Error Was Encountered
Unable to load the requested file: helpers/validation_helper.php

and my helper written like this

PHP Code:

<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');

if (!function_exists('Time_Validation'))
{
    function Time_Validation($data = FALSE)
    {
             //...
        }
} 


Ive tried to load my loader like

PHP Code:

$this->load->helper('validation'); 


And

PHP Code:

$this->load->helper('validation_helper'); 


My helper file started with small letter and I've tried to make it upper case (only the 'V') but still is the same.

Any Idea?

Thanks everybody