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"
`