I am currently working on an eCommerce website on Magento and I need to put a product countdown timer, this timer I want to show it only on those products that are on some kind of limited period offer and I want it to be on the category page and on the single product page. I know this can be easily done with the help of extension's but I am not keen to use any extension. I have searched the web for this solution but was not successful. If this can be done by manual coding using PHP or JavaScript then please help. Thanks in advance.
It is possible by coding.Just refer below link
http://www.magentoworks.net/magento-create-daily-deal-page-programmatically/
if you want to display timer on category page than you need to put code in list.phtml file also.