Every time I was running apt-get update I’d be asked to select the Area and Town/Zone my timezone was in, as part of the dpkg-reconfigure tzdata step.
If you run the command debconf-set-selections you can configure debconf’s internal database to store the defaults for the future.
The «EOF allows you to keep adding information until EOF is entered by itself on a line. This’ll set a few things - make sure you know which area and zone you want to use (you’ll have seen it when you get asked by tzdata).
There’s a list of tzdata zones on wikipedia or you can find a pairing in /usr/share/zoneinfo/* on Ubuntu.
Below is an example of me setting my location to Australia/Brisbane.