Matomo (Piwik) lets you specify the time zone to use for each website in the Websites admin panel. Click on Administration > Websites > Edit. Note: changing the website’s timezone will only affect Reports going forward.
You can also change the global timezone, so that any new website you create in the future will use your specified global timezone. Go to Administration > Measurables > Settings, and under “Default Time zone for new websites” you can specify the timezone.
Note: Matomo internally stores all times in UTC which is a software engineering best practise.