asp.net cookie genocide always 1/1/0001 12:00 am

i'm sourroundings cookie genocide controlling following code:

---

// mislay existent cookies.
request.cookies.clear();
response.cookies.clear();

// ... serialize encrypt information ...

// set cookie.
httpcookie cookie = new httpcookie(authcookiename, encrypted);
cookie.expires = datetime.now.add(timespan.fromhours(cookietimeouthours));
cookie.httponly = true;
response.cookies.add(cookie);

// route opposite page

---

when i review cookie timeout page i'm removing 1/1/0001 12:00 am. someone assistance me figure out problem, i'll conclude it. i'm controlling asp.net 3.5

ok. after reading links gulzar, appears i can't check cookie.expires httprequest during all? since links seem advise cookie.expires always set datetime.minvalue since server never know tangible fan machine? means i have store inside cookie myself check it? bargain correct?

thanks
shankar