Cookies having two expiry dates; which will be accepted.

Hi Guys, I have encountered a weird situation here. I can pass my strings in the Set-Cookie line of HTTP response headers, using a GET parameter. But still I am not able to put my own expiry date with cookie. Is it something which i can't do with request as server will be treating the whole input as cookie value. Or I am doing it in a wrong way. Below is the response line. Set-Cookie: xxx=yyyyyy; expires=Fri, 11-feb-2017 07:32:40; GMT path=/; expires=Fri, 26-Dec-2014 07:46:15 GMT; path=/; HttpOnly Here, yyyyyy; expires=Fri, 11-feb-2017 07:32:40; GMT path=/ , is what I have entered using the GET parameter. If someone has experience with this, please let me know.