[BUG] Documentation: TZ environment variable in docker compose seems to not work, APP_DISPLAY_TIMEZONE does

[Mesman-S]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

When setting up a Bookstack docker image in docker compose i tried to change the timezone settings. In https://hub.docker.com/r/linuxserver/bookstack/ the variable TZ is shown. However this

bookstack:
        image: lscr.io/linuxserver/bookstack:latest
        environment:
            TZ: Europe/Amsterdam

seems to have no effect, but using APP_DISPLAY_TIMEZONE does:

bookstack:
        image: lscr.io/linuxserver/bookstack:latest
        environment:
            APP_DISPLAY_TIMEZONE: Europe/Amsterdam

However the docker hub documentation only mentions TZ, does not mention APP_TIMEZONE and APP_DISPLAY_TIMEZONE that are mentioned here: https://www.bookstackapp.com/docs/admin/language-config/

Expected Behavior

Assuming my use of TZ: Europe/Amsterdam was correct but the ENV variable doesn't do anything:
remove mentions of TZ, and replace with mention of APP_DISPLAY_TIMEZONE

Steps To Reproduce

1. docker compose on linux, using bookstack latest image
2. attempt to change the display timezone with TZ
3. open bookstack and hover a timestamp, check to see which timezone is chosen for display
4. change ENV variable to APP_DISPLAY_TIMEZONE
5. open bookstack again, hover a timestamp and see that now it did take effect

Environment

- OS: CachyOS
- How docker service was installed: distro packagemanager

CPU architecture

x86-64

Docker creation

bookstack:
        image: lscr.io/linuxserver/bookstack:latest
        environment:
            APP_DISPLAY_TIMEZONE: Europe/Amsterdam

Container logs

migrations] started
[migrations] 01-nginx-site-confs-default: skipped
[migrations] 02-default-location: skipped
[migrations] done
───────────────────────────────────────

      ██╗     ███████╗██╗ ██████╗
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      ██║     ███████╗██║██║   ██║
      ██║     ╚════██║██║██║   ██║
      ███████╗███████║██║╚██████╔╝
      ╚══════╝╚══════╝╚═╝ ╚═════╝

   Brought to you by linuxserver.io
───────────────────────────────────────

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GID/UID
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User UID:    33
User GID:    33
───────────────────────────────────────
Linuxserver.io version: v26.03.3-ls256
Build-date: 2026-04-13T19:21:12+00:00
───────────────────────────────────────
    
using keys found in /config/keys
Waiting for DB to be available

   INFO  Nothing to migrate.  

[custom-init] No custom files found, skipping...
[ls.io-init] done.

[github-actions]

Thanks for opening your first issue here! Be sure to follow the relevant issue templates, or risk having this issue marked as invalid.

[aptalca]

Php has its own timezone setting which is only set during first run. If you want to change it later, you can edit the file php-local.ini in the config folder.