Timezone can easily be configured with the setup-timezone script.

The approach below is only convenient for systems that need frequent timezone changes, potentially while offline.

Manual configuration

Timezone data files are provided by te tzdata package. The current timezone is defined in the /etc/localtime file. To change the timezone, make this file a link to another timezone data file. For example:

apk add tzdata
ln -s /usr/share/zoneinfo/Europe/Brussels /etc/localtime