If you need check user time zones in the front end you can run different Chromium profiles with TZ parameter
TZ='America/Los_Angeles' chromium "--user-data-dir=$HOME/chrome-profile"
TZ='Asia/Tbilisi' chromium "--user-data-dir=$HOME/chrome-profile2"
TZ='Europe/London' chromium "--user-data-dir=$HOME/chrome-profile3"
TZ='Europe/Kiev' chromium "--user-data-dir=$HOME/chrome-profile4"
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