this is solved but i can't post my answer here... clicking submit takes me back to editor. no messages

ok. got excellent help at stack exchange and here is the solution - also posted here*

Specs: Centos 7.5, MariaDB 5.5, plesk 17.8

we need to load the timezones to mysql. (used this excellent post*)

i runand it returned null. this means time zones are not loaded.

so i logged with ssh and give

remember this is a plesk installation. use "-u root" and your mysql password if not plesk.
you may get 2 warnings

based on this* you are good to go.

now zones are loaded. you can run the previous query to test it.

and now we can use mick's query to convert the timezone properly.
@Fotis thank you for your help! using JDate, i think i tried it in the past. i couldn't come with any solution. if you have any suggestions i could happily try them.

*unfortunately links are not accepted by the editor so i had to delete them