SQL> select trunc((sysdate - to_date('01-01-1970','dd-mm-yyyy'))*24*60*60)
  2  from   dual;

TRUNC((SYSDATE-TO_DATE('01-01-1970','DD-MM-YYYY'))*24*60*60)
------------------------------------------------------------
                                                  1160755089

trunc((sysdate - to_date('01-01-1970','dd-mm-yyyy'))*24*60*60)

time 

The time, in seconds, when you generate the token data. Specify time as the number
of seconds from the epoch (midnight January 1, 1970), normalized to Greenwich
Mean Time (GMT). Specify time as base 10, without leading zeros or trailing decimals.
For example: 1139331600.
If your server’s clock is not synchronized with the iTunes U server, authentication fails.
To ensure that your time is synchronized with the iTunes U server time, set your
institution’s server time to network time (NTP).
iTunes U uses the token generation time to establish a login session. A login session
is the duration of time, 90 seconds by default, that your authentication and
authorization privileges are valid. If you access iTunes U after the token generation
time has expired, iTunes U directs you to the site’s login page. For a site available to
the public, iTunes U ignores the token, logs you in as a public visitor, and displays
only public information in the site.