The fpm-alpine image misses the tzdata package and does not handle the timezone correctly, leading to inconsistent behavior compared to apache and fpm.
docker run --rm -it -e "TZ=Europe/Luxembourg" postfixadmin:fpm date
Fri Mar 27 22:49:49 CET 2020
docker run --rm -it -e "TZ=Europe/Luxembourg" postfixadmin:fpm-alpine date
Fri Mar 27 21:49:56 UTC 2020