diff --git a/lib/http/cookie.rb b/lib/http/cookie.rb
index be06148..6282e3c 100644
--- a/lib/http/cookie.rb
+++ b/lib/http/cookie.rb
@@ -89,7 +89,7 @@ class HTTP::Cookie
 
   # The Expires attribute value as a Time object.
   #
-  # The setter method accepts a Time object, a string representation
+  # The setter method accepts a Time / DateTime object, a string representation
   # of date/time that Time.parse can understand, or `nil`.
   #
   # Setting this value resets #max_age to nil.  When #max_age is
@@ -493,6 +493,8 @@ class HTTP::Cookie
   def expires= t
     case t
     when nil, Time
+    when DateTime
+      t = t.to_time
     else
       t = Time.parse(t)
     end
diff --git a/test/test_http_cookie.rb b/test/test_http_cookie.rb
index 6f8ce87..a01b46a 100644
--- a/test/test_http_cookie.rb
+++ b/test/test_http_cookie.rb
@@ -717,8 +717,22 @@ class TestHTTPCookie < Test::Unit::TestCase
   end
 
   def test_expiration
-    cookie = HTTP::Cookie.new(cookie_values)
+    expires = Time.now + 86400
+    cookie = HTTP::Cookie.new(cookie_values(expires: expires))
 
+    assert_equal(expires, cookie.expires)
+    assert_equal false, cookie.expired?
+    assert_equal true, cookie.expired?(cookie.expires + 1)
+    assert_equal false, cookie.expired?(cookie.expires - 1)
+    cookie.expire!
+    assert_equal true, cookie.expired?
+  end
+
+  def test_expiration_using_datetime
+    expires = DateTime.now + 1
+    cookie = HTTP::Cookie.new(cookie_values(expires: expires))
+
+    assert_equal(expires.to_time, cookie.expires)
     assert_equal false, cookie.expired?
     assert_equal true, cookie.expired?(cookie.expires + 1)
     assert_equal false, cookie.expired?(cookie.expires - 1)