How to change the date of Linux to UTC/GMT +1?

The normal way is to set your timezone. There are a bunch of files stored by region in the following directory:

/usr/share/zoneinfo

Take a look and find the one which matches your region. Then you have to create a symlink from /etc/localtime:

sudo rm /etc/localtime
sudo ln -s /usr/share/zoneinfo/Europe/London /etc/localtime

You need to change the timezone.

• To do it system-wide, symlink /etc/localtime to the apropriate file in /usr/share/zoneinfo. For example:

  ln -sf /usr/share/zoneinfo/Europe/Paris /etc/localtime
  

  In CentOS, you might need to also edit /etc/sysconfig/clock.

• To change the timezone just for the current user, set $TZ instead:

  export TZ="Europe/Paris"
  

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Note that date -u must always return correct UTC time.