מאגר מידע

It's very easy, you first need to remove the current time file

rm /etc/localtime

and replace it by the new one, you need to search the biggest city in the area you want
Here is the list : https://www.archlinux.org/packages/core/any/tzdata/files/
for the example let's take :

/usr/share/zoneinfo/right/Europe/Amsterdam

you simply need to do the command : ln -s /usr/share/zoneinfo/right/Europe/Amsterdam /etc/localtime
Replace the red text by the line you wish

Here are some examples : 
for Cairo :

ln -s /usr/share/zoneinfo/right/Africa/Cairo /etc/localtime

for Berlin :

ln -s /usr/share/zoneinfo/right/Europe/Berlin /etc/localtime

And then you can check the time with the command : date