I'm having problems getting last update time(like I see sometimes in Update Manager).
Do you think it's possible to get from SSH a file/command that will show last update check for the current system ?
Thank you
Look at the /var/log/apt/history.log. This file contains information of when, what was updated and how long it took. The field 'Commandline' can also tell whether the update was run automatically or by hand.
To find out the time of last update check have a look at these files:
apt-get update
manually some time later