Use the XDATE command to supply a time stamp for the file being sent.
The XDATE statement should come after a FILE command and should preceed any DATA commands.

The syntax is
  XDATE     seconds  

where
seconds   is the age of the file in seconds since the epoch

The XDATE command represents the time and date as a single integral value,
the number of seconds since the epoch, January 1, 1970.