Schedule cron jobs with WordPress

Add This code in theme's function.php file...
<?php
add_action('my_hourly_event', 'do_this_hourly');
function my_activation() {
    if ( !wp_next_scheduled( 'my_hourly_event' ) ) {
         wp_schedule_event(time(), 'hourly', 'my_hourly_event');
    }
}
add_action('wp', 'my_activation');
function do_this_hourly() {
    // do something every hour
}
?>