This script downloads a given file from a webserver and compared the
timestamp in the file with the current time.
That allows to validate for example if the directory on the webserver
is synced often enough with the real source.
All that's needed for this script is a file that contains (in the first
body line) a timestamp in the form $(date +"%Y-%m-%d %H:%M:%%S"), for
example:'2017-11-25 20:00:00'. This line will be compared with the
current time.