Source: https://linuxize.com/post/how-to-set-or-change-timezone-on-ubuntu-20-04/

timedatectl

Ceci montre que le système est en UTC :

               Local time: Mon 2021-03-15 05:30:19 UTC
           Universal time: Mon 2021-03-15 05:30:19 UTC
                 RTC time: Mon 2021-03-15 05:30:20    
                Time zone: Etc/UTC (UTC, +0000)       
System clock synchronized: yes                        
              NTP service: active                     
          RTC in local TZ: no 

Lister les zones disponibles :

timedatectl list-timezones

Modifier la timezone du système :

sudo timedatectl set-timezone Europe/Brussels

Vérifier les changements :

timedatectl

               Local time: Mon 2021-03-15 06:36:02 CET 
           Universal time: Mon 2021-03-15 05:36:02 UTC 
                 RTC time: Mon 2021-03-15 05:36:03     
                Time zone: Europe/Brussels (CET, +0100)
System clock synchronized: yes                         
              NTP service: active                      
          RTC in local TZ: no