 <p>It is not. One is in seconds, the others in in microseconds, you you need to scale:</p> <pre><code>1393031459 &gt; (1377624200429 / 1000) </code></pre> <p>nsICookie2:</p> <pre><code>/** * the actual expiry time of the cookie, in seconds * since midnight (00:00:00), January 1, 1970 UTC. * * this is distinct from nsICookie::expires, which * has different and obsolete semantics. */ readonly attribute int64_t expiry; /** * the creation time of the cookie, in microseconds * since midnight (00:00:00), January 1, 1970 UTC. */ readonly attribute int64_t creationTime; /** * the last time the cookie was accessed (i.e. created, * modified, or read by the server), in microseconds * since midnight (00:00:00), January 1, 1970 UTC. * * note that this time may be approximate. */ readonly attribute int64_t lastAccessed; </code></pre> <p>Admittedly, it is quite confusing to use different time units. :p</p>