The digital clock is synchronized with internet servers, set to Europe/Madrid ZT (i.e. CET), but shows one hour more, at the time of posting this question it is 20:31. I've tried to remove and add it again, no changes. Have browsed for 'ZT=' in configuration user files, nothing shows up. Also run
sudo ntpdate ntp.ubuntu.com, and this is the answer:
24 Jan 20:32:10 ntpdate: the NTP socket is in use, exiting
Have no clue of what to do, since another laptop (same brand, model and configuration: HP ProBook 6360b, 16GB, 250GB SSD) was installed at the same time, and it shows the right time, at home under a private router; while this one is in a public institution. Both have Lubuntu 16.04 installed, alone.